averages Model Questions & Answers, Practice Test for ssc cgl tier 1 2023

Question :26

Average age of 36 children of the class is 15 years. 12 more children joined whose average age is 16 years. What is the average age of all the 48 children together?

Answer: (c)

Required average age = ${({15 × 36 + 12 × 16}/{36 + 12})}$

= $({540 + 192}/48)$ years = $({732}/{48})$ years = 15.25 years.

Question :27

The age of a man is three times the sum of the ages of his two sons. Five years hence, his age will be double of the sum of the ages of his sons. The father's present age is

Answer: (a)

Let the father's present age be x and son's age be x 1 and x 2 .

Now, x = 3$(x_1 + x_2)$ .....(i)

Also, x + 5 = 2$(x_1 + 5 + x_2 + 5)$

x + 5 = 2$(x_1 + x_2 + 10)$ .....(ii)

Putting value of $(x_1 + x_2) = x/3$ from (i) in equation (ii)

x + 5 = 2 $({x/3} + 10)$ = 45

Question :28

Eighteen years ago, a father was three times as old as his son. Now the father is only twice as old as his son. Then the sum of the present ages of the son and the father is:

Answer: (b)

Let the present ages of the father and son be 2x and x years respectively.

Then, (2x – 18) = 3 (x – 18)⇔x = 36.

∴ Required sum = (2x + x) = 3x = 108 years.

Question :29

The ratio between the present ages of P and Q is 3 : 4 respectively. Four years hence Q will be 5 years older than P. What is P's present age?

Answer: (c)

Let the present ages of P and Q be 3x and 4x respectively.

After 4 years

4x – 3x = 5

∴ x = 5

∴ P's present age = 3x = 3 × 5 = 15 years

Question :30

The average age of a man and his son is 16 years. The ratio of their ages is 15 : 1 respectively. What is the son's age?

Answer: (d)

Let the age of father and son be 15x years and x years respectively.

Now, according to the question, ${15x + x}/2 = 16$

or, x ${16 × 2}/16$ = 2years

Hence age of the son = 2 years

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