1. The average age of 24 students and the principal is 15 years. When the principal’s age is excluded, the average age decreases by 1 year. What is the age of the principal?
(a) 38
(b) 40
(c) 39
(d) 37
2. The average weight of 3 men A, B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man E, whose weight is 3 kg more than that of D, replaces A then the average weight of B, C, D and E becomes 78 kg. The weight of A is
(a) 70 kg
(b) 72 kg
(c) 79 kg
(d) 78 kg
3. The mean temperature of Monday to Wednesday was 37 °C and of Tuesday to Thursday was 34 °C. If the temperature on Thursday was 4/5 that of Monday, the temperature on Thursday was
(a) 38 °C
(b) 36 °C
(c) 40 °C
(d) 39 °C
4. Three years ago, the average age of A, B and C was 27 years and that of B and C 5 years ago was 20 years. A’s present age is
(a) 30 years
(b) 35 years
(c) 40 years
(d) 48 years
5. Sachin Tendulkar has a certain average for 9 innings. In the tenth inning, he scores 100 runs thereby increasing his average by 8 runs. His new average is
(a) 20
(b) 24
(c) 28
(d) 32
(a) 20
(b) 21
(c) 28
(d) 30
7. There are three fractions A, B and C. If A = 1/4 and B = 1/6 and the average of A, B and C is 1/12. What is the value of C?
(a) –1/2
(b) – 1/6
(c) –1/3
(d) – 1/4
8. The marks obtained by Hare Rama in Mathematics, English and Biology are respectively 93 out of 100, 78 out of 150 and 177 out of 200. Find his average score in percent.
(a) 87.83
(b) 86.83
(c) 76.33
(d) 77.33
9. The average monthly expenditure of a family was ` 2750 for the first 3 months, 3150 for the next three months and ` 6750 for the next three months. Find the average income of the family for the 9 months, if they save 650 per month.
(a) 4866.66
(b) 5123.33
(c) 4666.66
(d) 4216.66
10. The average age of a family of 6 members is 22 years. If the age of the youngest member be 7 years, what was the average age of the family at the birth of the youngest member?
(a) 15
(b) 18
(c) 21
(d) 12
Answers:-
1. (c)
2. (c)
3. (b)
4. (c)
5. (c)
6. (b)
7. (b)
8. (d)
9. (a)
10. (b)
Solutions:-
1. P = 25 × 15 – 24 × 14 = 375 – 336 = 39
2. D’s weight = 4 × 80 – 3 × 84 = 320 – 252 = 68. E’s weight = 68 + 3 = 71.
Now, we know that A + B + C + D = 4 × 80 = 320 and B + C + D + E = 78 × 4 = 312. Hence, A’s
weight is 8 kg more than E ’s weight. A = 71 + 8 = 79.
3. Monday + Tuesday + Wednesday = 3 × 37 = 111;
Tuesday + Wednesday + Thursday = 3 × 34 = 102. Thus, Monday – Thursday = 9 and
Thursday = 4 × Monday/5 Æ Thursday = 36 and Monday = 45.
4. Today’s total age of A, B and C = 30 × 3 = 90.
Today’s total age for B and C = 25 × 2 = 50.
C ’s age = 90 – 50 = 40.
5. 9x + 100 = 10(x + 8) Æ x = 20 (average after 9 innings). Hence, new average = 20 + 8 = 28.
6. 7 × 3 = 21.
7. 1/4 + 1/6 + C = 3 × 1/12 Æ C = –1/6.
8. His total score is 93 + 78 + 177 = 348 out of 450. % score = 77.33
9. Average income over 9 months = [3 × (2750 + 650) + 3 × (3150 + 650) + 3 × (6750+650)]/9
= [3 × 3400 + 3 × 3800 + 3 × 7400]/9 = 4866.66
10. Today’s total age = 6 × 22 = 132 years. Total age of the family excluding the youngest member
(for the remaining 5 people) = 132 – 7 = 125. Average age of the other 5 people in the family = 25
years.
7 years ago their average age = 25 – 7 =18 years.
