# Top 100+ Average Aptitude Questions and Answers - 1

Question: 1

The average age of 30 students is 9 years. If the age of their teacher is included, it becomes 10 years. The age of the teacher (in years) is

(A) 31

(B) 35

(C) 40

(D) 43

Ans: C

Age of teacher = (31 × 10 – 30 × 9)

= 40 years.

Question: 2

The average weight of 10 men is decreased by 3 kg when one of them whose weight is 80 kg is replaced by a new person. The weight of the new person is

(A) 50

(B) 60

(C) 70

(D) 73

Ans: A

Average decrease of weight by replacement of 1 man = 3 kg.

Average decrease of weight by replacement of 10 men = 3 x 10 = 30 kg.

The weight of man replaced = 80 kg.

∴ Weight of new man = 80 kg – 30 kg = 50 kg.

Question: 3

The average of 17 numbers is 45. The average of first 9 of these numbers is 51 and the last 9 of these numbers is 36. What is the ninth number?

(A) 14

(B) 16

(C) 18

(D) 20

Ans: C

Total of 17 numbers = 17 x 45 = 765

Total of first 9 numbers = 9 x 51 = 459

Total of last 9 numbers = 9 x 36 = 324

∴ Tenth number = ( 459 + 324) – 765= 783 – 765

= 18.

Question: 4

The average weight of 9 mangoes increases by 20 gm if one of them weighing 120 gm is replaced by another. The weight of the new mango is

(A) 180 gm

(B) 200 gm

(C) 300 gm

(D) 360 gm

Ans: C

Total weight increased = (9 × 20 ) gm = 180 gm

Weight of new mango = ( 120 + 180) gm = 300 gm.

Question: 5

The average age of boys in the class is twice the number of girls in the class. If the ratio of boys and girls in the class of 36 be 5 : 1. What is the total of the ages (in years) of the boys in the class?

(A) 196

(B) 360

(C) 420

(D) 490

Ans: B

Number of boys = $$(36 × {5} / {6})$$ = 30.

Number of girls = 6.

Average age of boys = ( 2 x 6 ) = 12 years.

∴ Total age of boys = ( 12 x 30) = 360 years.

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