**Average Aptitude Set 2**

**6) Average age of a group of 30 boys is 16 years. A boy of age 19 leaves the group and a new boy joins the group. If the new average age of the group is 15.8 years, find the age of the new boy.**

- 12 years
- 13 years
- 14 years
- 15 years

The correct answer is **B**

**Explanation:**

Let the age of new boy = X years

Total age of 30 boys = 30*16 = 480 years

As per question, if we minus age of boy who leaves the group and then add the age of boy who joins the group the new average becomes = 15.8 years.

∴

480 – 19 + X = 474

X = 474 – 480 +19

X = – 6 +19

= 13 years

**7) The average weight of 10 men is decreased by 2 kg when one of them whose weight is 60 kg is replaced by a new man. What is the weight of the new man?**

- 35 kg
- 40 kg
- 45 kg
- 50 kg

The correct answer is **B**

**Explanation:**

Average decrease in weight per person = 2kg

There are 10 men so total decrease in weight on replacing a man with a new man = 10 ∗ 2= 20 kg

Weight of the man who is replaced = 60 kg

∴The weight of the new man would be = Weight of man replaced – total decrease in weight of the group of 10 men.

= 60 – 20 = 40 kg

**8) The average age of 30 boys in a class is 15 years. If we include the age of two teachers the average age increases by 1. Find the sum of ages of the two teachers.**

- 55 years
- 58 years
- 62 years
- 64 years

The correct answer is **C**

**Explanation:**

Total age of 30 boys would be = 30∗15 = 450 years

Total age of 30 boys and 2 teachers would be = 32∗16= 512 years

∴ Sum of ages of two teachers would be = 512 – 450 = 62 years

**9) The average age of the committee of 10 members is 40 years. A member of age 52 retires and a new member of age 38 takes his place. What is the average age of the present committee?**

- 38.6 years
- 33.5 years
- 35.5 years
- 37.5 years

The correct answer is **A**

**Explanation:**

Total age of the committee = 10 ∗ 40 = 400 years

Age of retired member = 52 years

Age of new member = 38 years

As per question, we will minus 52 years and add 38 years in the total age then divide by 10 to find the new average age of the committee.

∴

=

**10) Four years ago, the average age of A and B was 20 years. If today average age of A, B and C is 25 years, what will be age of C after 7 years?**

- 32 years
- 34 years
- 36 years
- 38 years

The correct answer is **B**

**Explanation:**

Total age of A and B four years ago = 20 ∗ 2 = 40 years

Present total age of A and B would be = 40 + 4∗2 = 48 years

Present total age of A, B and C is = 25 ∗ 3 = 75 years

∴ Present age of C would be = 75 – 48 = 27 years

Age of C after 7 years = 27 + 7 = 34 years

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