AVERAGES EXAMPLE QUESTIONS PART 2
51.
The average price of 10 books is Rs.12 while the average price of 8 of these books is Rs.11.75. Of the remaining two books, if the price of one book is 60% more than the price of the other, what is the price of each of these two books?
A. Rs. 5, Rs.8
B. Rs. 8, Rs. 12.8
C. Rs. 10, Rs. 16
D. Rs. 12, Rs. 19.2
Solution:
Option(C) is correct
Total cost of 10 books = Rs. 120
Total cost of 8 books = Rs. 94
⇒⇒ The cost of 2 books = Rs. 26
Let the price of each book be x and y.
⇒ x + y = 26 ---------------- (1)
Given that the price of 1 book is 60% more than the other price
160y/100+y=26
y=26×100/260
y=10
Substituting Y=10 in (1) we get,
x+10=26
x = 16
52.
In a set of three numbers, the average of first two numbers is 2, the average of the last two numbers is 3, and the average of the first and the last numbers is 4. What is the average of three numbers?
A. 2
B. 2.5
C. 3
D. 3.5
Solution:
Option(C) is correct
Let the three numbers be x,y, and z. We are given that
x+y/2=2x+y2=2
y+z/2=3y+z2=3
x+z/2=4x+z2=4
Summing the three equations yields
(x+y/2)+(y+z/2)+(x+z/2)=2+3+4
x+y+z=9
The average of the three numbers is
=x+y+z/3
=9/3=3.
53.
The average monthly salary of 12 workers and 3 managers in a factory was Rs. 600. When one of the manager whose salary was Rs. 720, was replaced with a new manager, then the average salary of the team went down to 580. What is the salary of the new manager?
A. 570
B. 420
C. 690
D. 640
Solution:
Option(B) is correct
The total salary amount = 15×600=9000
The salary of the exiting manager = 720.
Therefore, the salary of 12 workers and the remaining 2 managers:
=9000−720=8280
When a new manager joins, the new average salary drops to Rs.580 for the total team of 15 of them.
The total salary for the 15 people i.e., 12 workers, 2 old managers and 1 new manager = 580×15=8700
Therefore, the salary of the new manager is 9000−8700=300 less than that of the old manager who left the company, which is equal to 720−300=420.
Another alternate method of doing the problem is as follows:
The average salary dropped by Rs.20 for 15 of them. Therefore, the overall salary has dropped by 15×20=300.
Therefore, the new manager's salary should be Rs.300 less than that of the old manager =720−300=420.
54.
In Arun's opinion, his weight is greater than 65 kg but less than 72 kg. His brother does not agree with Arun and he thinks that Arun's weight is greater than 60 kg but less than 70 kg. His mother's view is that his weight cannot be greater than 68 kg. If all are them are correct in their estimation, what is the average of different probable weights of Arun?
A. 67 kg.
B. 68 kg.
C. 69 kg.
D. Data inadequate
Solution:
Option(A) is correct
Let Arun's weight by X kg.
According to Arun:
65<X<72
According to Arun's brother:
60<X<70.
According to Arun's mother:
X<=68
The values satisfying all the above conditions are 66, 67 and 68.
Required average
=66+67+68=201/3=67 kg.
55.
A student finds the average of 10 positive integers. Each integer contains two digits. By mistake, the boy interchanges the digits of one number say ba for ab. Due to this, the average becomes 1.8 less than the previous one. What was the difference of the two digits aa and bb?
A. 8
B. 6
C. 2
D. 4
Solution:
Option(C) is correct
Let the original number be abab i.e., (10a+b)
After interchanging the digits, the new number becomes ba i.e., (10b+a)
The question states that the average of 10 numbers has become 1.8 less than the original average.
Therefore, the sum of the original 10 numbers will be 10×1.8 more than the sum of the 10 numbers with the digits interchanged.
i.e., 10a+b=10b+a+18
9a−9b=18
a−b = 2
56. Find the average of numbers 87, 84, 86, 90, 82, 88, 78.
A. 85
B. 84
C. 83
D. 82
Answer & Explanation
Sol : Option A
The sum of all the observations here is 87 + 84 + 86 + 90 +82 + 88 +78 = 595
Number of observations = 7
So, Average = 595/7 = 85
57. The average of 4 terms is 20 and the 1st term is 1/3 of the remaining terms. What will be the first number?
A. 30
B. 20
C. 60
D. 80
Answer & Explanation
Sol : Option B
Average of 4 terms = 20
Hence, the total sum of 4 terms = 80
Let terms be A,B,C,D
So, the sum will be A+B+C+D =80
Given, 3A = B+C+D
So, 4A = 80,
A = 20
58. The average age of A, B and C was 25 years and that of B and C was 25 years. A’s present age is:
A. 30 years
B. 25 years
C. 40 years
D. 42 years
Answer & Explanation
Sol : Option B
Average of A,B,C is 25
So, sum of their ages =75
Now, the sum of B and C will be 50 (because their average is 25)
So age of A =75 - 50 = 25 years
59. The average of 7 consecutive numbers is n. If the next two numbers are included, the average will
A. increased by 2
B. remains the same
C. increased by 1
D. increased by 2
Answer & Explanation
Sol : Option C
The average of 7 consecutive numbers is n implies that the 4th term is equal to n.
Now if we include next two terms then the average of 9 terms will be the 5th term. Now as the terms are consecutive, so the 5th term will be n + 1.
60. For 9 innings, Boman has an average of 75 runs. In the tenth inning, he scores 100 runs, thus increasing his average . His new average is
A. Rs. 75
B. Rs. 100
C. Rs. 72
D. Rs. 77.5
Answer & Explanation
Sol : Option D
Total score for 9 innings is 75×9 = 675
Total score after 10th innings = 675 + 100 = 775
So, average = 775 / 10 = 77.5
61. For 9 innings, Roman has an average of 65 runs. In the tenth inning, he scores 200 runs, thus increasing his average . His average increased by
A. 78.5
B. 72
C. 13.5
D. 77.5
Answer & Explanation
Sol : Option C
Total score for 65 innings = 65×9 = 585
Total score after 10th innings = 585 + 200 = 785
So, the new average is 785/10 = 78.5
So, the increment is of 13.5
62. In a family of 8, the men eat on average 72kg of food and women eat on an average 50kg of food. The men and women are equal in number. A hungry woman named Neetu joined the family for dinner and the average consumption became 67.How much did Neetu eat (in kgs)?
A. Rs. 115
B. Rs. 80
C. Rs. 90
D. Rs. 85
Answer & Explanation
Sol : Option A
As men and women are equal so , there are 4 women and 4 men so, total consumption will be 72×4 = 288(by men) and 50×4 = 200(by women)
Total consumption = 488.
But after including Neetu the average consumption for 9 people is given to be 67.So the total consumption will be 67×9 = 603. So, Neetu’s consumption will be = 603 – 488 = 115.
63. In a hotel, the tariff for every odd dates is Rs.1000 and for even dates is Rs. 2000. If the man paid total of 30000 in all. For how many days did he stay in the hotel given that the first day is 5th date of the month?
A. 50
B. 20
C. 40
D. 60
Answer & Explanation:
Sol : Option B
Total tariff = 30000
So, for odd dates (5th , 7th , and so on) = 1000
And for even dates (6th , 8th and so on ) = 2000
So, the average amount of money for 2 days is Rs. 1500.
So, total amount paid = 30000
So , number of days he stayed in the hotel = 30000/1500 = 20.
64. The average of 5 terms is 50. If the first 4 terms are 45, 42, 119, and 84, what will be the last term?
A. 56
B. -20
C. -40
D. -50
Answer & Explanation
Sol : Option C
Sum of all the terms = 250
Sum of first four terms = 45+42+119+84 = 290
So, the 5th term should be 250 – 290 = - 40.
65. If the average number of 8 terms is given to be 40 and the average of first 6 terms is given to be 35.What is the average of the remaining 2 terms?
A. 30
B. 55
C. 40
D. 42
Answer & Explanation
Sol : Option B
Sum of all the 8 terms = 320.
The sum of first 6 terms = 210
Now , the sum of remaining terms = 320 – 210 = 110
So , the average of 2 terms would be = 110/2 = 55
66. The average of first 10 even numbers is?
• A. 18
• B. 22
• C. 9
• D. 11
Answer & Explanation
Answer: Option D
Explanation:
Sum of 10 even numbers = 10 * 11 = 110
Average = 110/10 = 11
67. The average of 11 numbers is 10.9. If the average of first six is 10.5 and that of the last six is 11.4 the sixth number is?
• A. 11.0
• B. 11.3
• C. 11.4
• D. 11.5
Answer & Explanation
Answer: Option D
Explanation:
1 to 11 = 11 * 10.9 = 119.9
1 to 6 = 6 * 10.5 = 63
6 to 11 = 6 * 11.4 = 68.4
63 + 68.4 = 131.4 – 119.9 = 11.5
6th number = 11.5
68. The average of first ten prime numbers which are odd is?
• A. 12.9
• B. 13.8
• C. 17
• D. 15.8
Answer & Explanation
Answer: Option D
Explanation:
Sum of first 10 prime no. which are odd = 158
Average = 158/10 = 15.8
69. The average of first 10 natural numbers is?
• A. 5
• B. 5.5
• C. 6.5
• D. 6
Answer & Explanation
Answer: Option B
Explanation:
Sum of 10 natural no. = 110/2 = 55
Average = 55/10 = 5.5
70. The average of first 10 odd numbers is?
• A. 11
• B. 10
• C. 17
• D. 9
Answer & Explanation
Answer: Option B
Explanation:
Sum of 10 odd no. = 100
Average = 100/10 = 10
71. The sum of five numbers is 655. The average of the first two numbers is 85 and the third number is 125. Find the average of the two numbers?
• A. 180
• B. 170
• C. 190
• D. 175
• E. None of these
Answer & Explanation
Answer: Option A
Explanation:
Let the five numbers be P, Q, R, S and T.
=> P + Q + R + S + T = 655.
(P + Q)/2 = 85 and R = 125
P + Q = 170 and R = 125
P + Q + R = 295
S + T = 655 - (P + Q + R) = 360
Average of the last two numbers = (S + T)/2 = 180.
72. The average amount with a group of seven numbers is Rs. 20. If the newly joined member has Rs. 50 with him, what was the average amount with the group before his joining the group?
• A. Rs. 25
• B. Rs. 18
• C. Rs. 15
• D. Rs. 22
• E. None of these
Answer & Explanation
Answer: Option C
Explanation:
Total members in the group = 7
Average amount = Rs. 20
Total amount with them = 7 * 20 = Rs. 140
One number has Rs. 50. So, the amount with remaining 6 people = 140 - 50 = Rs. 90
The average amount with them = 90/6 = Rs. 15.
73. The average weight of a group of boys is 30 kg. After a boy of weight 35 kg joins the group, the average weight of the group goes up by 1 kg. Find the number of boys in the group originally ?
• A. 4
• B. 5
• C. 6
• D. 7
• E. None of these.
Answer & Explanation
Answer: Option A
Explanation:
Let the number off boys in the group originally be x.
Total weight of the boys = 30x
After the boy weighing 35 kg joins the group, total weight of boys = 30x + 35
So 30x + 35 + 31(x + 1) = > x = 4.
74. The average runs scored by a batsman in 20 matches is 40. In the next 10 matches the batsman scored an average of 13 runs. Find his average in all the 30 matches?
• A. 31
• B. 29
• C. 28
• D. 30
• E. None of these
Answer & Explanation
Answer: Option A
Explanation:
Total score of the batsman in 20 matches = 800.
Total score of the batsman in the next 10 matches = 130.
Total score of the batsman in the 30 matches = 930.
Average score of the batsman = 930/30 = 31.
75. The average age of seven persons sitting in a row facing east is 28 years. If the average age of the first three persons is 21 years and the average age of the last three persons is 34 years, then find the age of the person sitting in the middle of the row?
• A. 30 Years
• B. 31 years
• C. 26 years
• D. 33 years
• E. None of these
Answer & Explanation
Answer: Option B
Explanation:
Total age seven persons = (28 * 7)years
Total age of the first three persons and the last three persons are (21 * 3) years and (34 * 3) years respectively.
Age of the person sitting in the middle of the row = 28 * 7 - 21 * 3 - 34 * 3 = 196 - 63 - 102 = 31 years.
76. The average height of 35 boys in a class was calculated as 180cm. It has later found that the height of one of the boys in the class was wrongly written as 166 cm whereas his actual height was 106 cm. Find the actual average height of the boys in the class (Round off your answer to two decimal places).
• A. 179.29 cm
• B. 178.29 cm
• C. 179.38 cm
• D. 178.39 cm
• E. None of these
Answer & Explanation
Answer: Option B
Explanation:
Calculated average height of 35 boys = 180 cm.
Wrong total height of 35 boys = 180 * 35 cm. This was as a result of an actual height of 106 cm being wrongly written as 166 cm. Correct total height of 35 boys = 180 * 35 cm - 166 cm + 106 cm
= 180 * 35 cm - 166 cm + 106 cm/35 = 180 cm - 60 /35 cm
= 180 cm - 1.71 cm = 178.29 cm.
77. The total marks obtained by a student in Physics, Chemistry and Mathematics is 150 more than the marks obtained by him in Physics. What is the average mark obtained by him in Chemistry and Mathematics?
• A. 75
• B. 150
• C. 50
• D. Cannot be determined
• E. None of these
Answer & Explanation
Answer: Option A
Explanation:
Let the marks obtained by the student in Physics, Chemistry and Mathematics be P, C and M respectively.
P + C + M = 150 + P
C + M = 150
Average mark obtained by the student in Chemistry and Mathematics = (C + M)/2 = 150/2 = 75.
78. The present average age of a family of five members is 26 years. If the present age of the youngest member in the family is ten years, then what was the average age of the family at the time of the birth of the youngest member ? (Assume no death occurred in the family since the birth of the youngest)
• A. 18 years
• B. 14 years
• C. 20 years
• D. 16 years
• E. None of these
Answer & Explanation
Answer: Option C
Explanation:
Present total age of the members = 26(5) = 130 years.
Present age of the youngest member = 10 years
Present total age of the remaining four members = 130 -10 = 120 years
Their average age at the time of the birth of the youngest member = [120 - (4 * 10)] / 4 = 30 - 10 = 20 years.
79. The average of four positive integers is 69. The highest integer is 93 and the least integer is 39. The difference between the remaining two integers is 28. Which of the following integers is the higher of the remaining two integers?
• A. 58
• B. 86
• C. 49
• D. Cannot be determined
• E. None of these
Answer & Explanation
Answer: Option B
Explanation:
Let the four integers be A, B, C and D where A > B > C > D.
(A + B + C + D)/4 = 69 => A + B + C + D = 276 ---> (1)
A = 93, D = 39 and B - C = 28
(1) => B + C = 276 - (A + D) = 276 - 132 = 144.
B + B -28 = 144
B = (144 + 28)/2 = 86
80. The average monthly income of P and Q is Rs. 5050. The average monthly income of Q and R is 6250 and the average monthly income of P and R is Rs. 5200. The monthly income of P is:
• A. Rs. 3500
• B. Rs. 4000
• C. Rs. 4050
• D. Rs. 5000
Answer & Explanation
Answer: Option B
Explanation:
Let P, Q and R represent their respective monthly incomes. Then, we have:
P + Q = (5050 * 2) = 10100 --- (i)
Q + R = (6250 * 2) = 12500 --- (ii)
P + R = (5200 * 2) = 10400 --- (iii)
Adding (i), (ii) and (iii), we get:
2(P + Q + R) = 33000 = P + Q + R = 16500 --- (iv)
Subtracting (ii) from (iv), we get, P = 4000.
P's monthly income = Rs. 4000.
81. The average monthly salary of 20 employees in an organisation is Rs. 1500. If the manager's salary is added, then the average salary increases by Rs. 100. What is the manager's monthly salary?
• A. Rs. 2000
• B. Rs. 2400
• C. Rs. 3600
• D. Rs. 4800
Answer & Explanation
Answer: Option C
Explanation:
Manager's monthly salary
= Rs. (1600 * 21 - 1500 * 20) = Rs. 3600
82. The captain of a cricket team of 11 members is 26 years old and the wicket keeper is 3 years older. If the ages of these two are excluded, the average age of the remaining players is one year less than the average age of the whole team. What is the average of the team?
• A. 23 years
• B. 24 years
• C. 25 years
• D. None of these
Answer & Explanation
Answer: Option A
Explanation:
Let the average of the whole team be x years.
11x - (26 + 29) = 9(x - 1)
= 11x - 9x = 46
= 2x = 46 => x = 23
So, average age of the team is 23 years.
83. A cricketer has a certain average for 10 innings. In the eleventh inning, he scored 108 runs, there by increasing his average by 6 runs. His new average is:
• A. 48 runs
• B. 52 runs
• C. 55 runs
• D. 60 runs
Answer & Explanation
Answer: Option A
Explanation:
Let average for 10 innings be x. Then,
(10x + 108)/11 = x + 6
= 11x + 66 = 10x + 108
= x = 42.
New average = (x + 6) = 48 runs.
84. A cricketer whose bowling average is 12.4 runs per wicket takes 5 wickets for 26 runs and there by decreases his average by 0.4. The number age of the family now is:
• A. 64
• B. 72
• C. 80
• D. 85
Answer & Explanation
Answer: Option D
Explanation:
Let the number of wickets taken till the last match be x. Then,
(12.4x + 26)/(x + 5) = 12
= 12.4x + 26 = 12x + 60
= 0.4x = 34
= x = 340/4 = 85.
85. The average age of a husband, wife and their child 3 years ago was 27 years and that of wife and the child 5 years ago was 20 years. The present age of the husband is:
• A. 19 years
• B. 23 years
• C. 28.5 years
• D. 29.3 years
• Answer & Explanation
Answer: Option A
Explanation:
Sum of the present ages of husband, wife and child = (23 * 2 + 5 * 2) = 57 years.
Required average = 57/3 = 19 years.
86. The average age of husband, wife and their child 3 years ago was 27 years and that of wife and the child 5 years ago was 20 years. The present age of the husband is:
• A. 35 years
• B. 40 years
• C. 50 years
• D. None of these
Answer & Explanation
Answer: Option B
Explanation:
Sum of the present ages of husband, wife and child = (27 * 3 + 3 * 3) = 90 years.
Sum of the present age of wife and child = (20 * 2 + 5 * 2) = 50 years.
Husband's present age = (90 - 50) = 40 years.
87. The arithmetic mean of the scores of a group of students in a test was 52. The brightest 20% of them secured a mean score of 80 and the dullest 25% a mean score of 31. The mean score of remaining 55% is:
• A. 45
• B. 50
• C. 51.4 approx.
• D. 54.6 approx.
Answer & Explanation
Answer: Option C
Explanation:
Let the required means score be x. Then,
20 * 80 + 25 * 31 + 55 * x = 52 * 100
= 1600 + 775 + 55x = 5200
= 55x = 2825
= x = 565/11 = 51.4.
88. The average salary of all the workers in a workshop is Rs. 8000. The average salary of 7 technicians is Rs. 12000 and the average salary of the rest is Rs. 6000. The total number of workers in the workshop is:
• A. 20
• B. 21
• C. 22
• D. 23
Answer & Explanation
Answer: Option B
Explanation:
Let the total number of workers be x. Then,
8000x = (12000 * 7) + 6000(x - 7)
2000x = 42000
x = 21.
89. In an examination a pupil's average marks were 63 per paper. If he had obtained 20 more marks for his Geography paper and 2 more marks for his History paper, his average per paper would have been 65. How many papers were there in the examination?
• A. 8
• B. 9
• C. 10
• D. 11
Answer & Explanation
Answer: Option D
Explanation:
Let the number of papers be x. Then,
63x + 20 + 2 = 65x
= 2x = 22
= x = 11.
90. The average age of students of a class is 15.8 years. The average age of boys in the class is 16.4 years and that of the girls is 15.4 years. The ration of the number of boys to the number of girls in the class is:
• A. 1:2
• B. 2:3
• C. 3:4
• D. 3:5
Answer & Explanation
Answer: Option B
Explanation:
Let the ratio be k : 1. Then,
k * 16.4 + 1 * 15.4 = (k + 1) * 15.8
= (16.4 - 15.8)k = (15.8 - 15.4)
= k = 0.4/0.6 = 2/3
Required ratio = 2/3 : 1 = 2:3.
91. The average of women and child workers in a factory was 15%yr. The average age of all the 16 children was 8yr and average age of women workers was 22 yrs if ten women workers were married then the number of unmarried women workers were
• A. 16
• B. 12
• C. 8
• D. 6
Answer & Explanation
Answer: Option D
Explanation:
Let the number of women workers be x
According to the question 22*x+16*8 = 15(16+x)
=> 22x+128 =240 +15x
=> 22x-15x = 240 -128
=> 7x=112
Therefore, x=112/7 =16
Therefore, Unmarried women workers =(16-10) =6
92. The mean marks of 30 students in a class is 58.5. Later on it was found that 75 was wrongly recorded as 57. Find the correct them.
• A. 57.4
• B. 57.5
• C. 58.9
• D. 59.1
Answer & Explanation
Answer: Option D
Explanation:
Correct mean = 30x 58.5 -57 +75/30
= 1755+18/30 = 1773/30
=59.1
93. A person travels from x to y at a speed of 40Km/h and returns by increasing his speed 50%. What is his average speed for both the trips?
• A. 36km/h
• B. 45km/h
• C. 48km/h
• D. 50km/h
Answer & Explanation
Answer: Option C
Explanation:
Speed of person from x to y =40 km/h
Speed of person from y to x =(40x150)/100 = 60km/h
Since the distance travelled is same
Therefore, Average Speed = (2x40x60)/40+60 = 48km/h
94. The average of 18 observations was calculated and it was 124. Later on it was discovered that two observations 46 and 82 were incorrect. The correct values are 64 and 28. The correct average of 18 observations is
• A. 123
• B. 137
• C. 121
• D. 122
Answer & Explanation
Answer: Option D
Explanation:
Sum of 18 observations = 18x124 =2232
Correct sum of 18 observations = 2232-46-82+64+28
= 2196
Therefore, Correct average =2196/18 = 122.
95. The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:
• A. 17 kg
• B. 20 kg
• C. 26 kg
• D. 31 kg
Answer & Explanation
Answer: Option D
Explanation:
Let A, B, C represent their respective weights. Then, we have: A + B + C = (45 x 3) = 135 .... (i) A + B = (40 x 2) = 80 .... (ii) B + C = (43 x 2) = 86 ....(iii) Adding (ii) and (iii), we get: A + 2B + C = 166 .... (iv) Subtracting (i) from (iv), we get : B = 31. B's weight = 31 kg.
96. The average of the two-digit numbers, which remain the same when the digits interchange their positions, is:
• A. 33
• B. 44
• C. 55
• D. 66
Answer & Explanation
Answer: Option C
Explanation:
Average = (11 + 22 + 33 + 44 + 55 + 66 + 77 + 88 + 99)/9
= [(11 + 99) + (22 + 88) + (33 + 77) + (44 + 66) + 55]/9
= [(4 * 110) + 55]/9 = 495/9 = 55.
97. The average of non-zero number and its square is 5 times the number. The number is:
• A. 9
• B. 17
• C. 29
• D. 295
Answer & Explanation
Answer: Option A
Explanation:
Let the number be x. Then,
(x + x2)/2 = 5x => x2 - 9x = 0
=> x(x - 9) = 0
=> x = 0 or x = 9
So, the number is 9.
98. A family consists of grandparents, parents and three grandchildren. The average age of the grandparents is 67 years, that of the parents is 35 years and that of the grandchildren is 6 years. What is the average age of the family?
• A. 28 4/7 years
• B. 31 5/7 years
• C. 32 1/7 years
• D. None of these
Answer & Explanation
Answer: Option B
Explanation:
Required Average = [(67 * 2) + (35 * 2 ) + (6 * 3)]/(2 + 2 + 3)
= (134 + 70 + 18)/7 = 31 5/7 years.
99. A library has an average of 510 visitors on Sunday and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is:
• A. 250
• B. 276
• C. 280
• D. 285
Answer & Explanation
Answer: Option D
Explanation:
Since the month begins with a Sunday, so there will be five Sundays in the month.
Required average = [(510 * 5) + (240 * 25)]/30 = 8550/30 = 285.
100. Five years ago the average of the ages of A and B was 40 years and now the average of the ages of B and C is 48 years. What will be the age of the B ten years hence?
• A. 55 years
• B. 56 years
• C. 58 years
• D. Data inadequate
• E. None of these
Answer & Explanation
Answer: Option D
Explanation:
Let the present ages of A, B and C be a, b and c respectively.
Given, [(a - 5) + (b - 5)] / 2 = 40 => a + b = 90 --- (1)
(b + c)/2 = 48 => b + c = 96 --- (2)
From (1) and (2), we cannot find b.
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