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

Answer: (e)

25a + 25b = 115

a + b = $115/25$ = 4.6

∴ Average of a and b = $4.6/2 = 2.3$

Answer: (c)

Age of the fourth friend

= 31 × 4 – 32 × 3

= 124 – 96 = 28 years

Alternatively (1 × 32) – (1 × 4) = 28 yrs.

Answer: (c)

Let the ratio of proportionality be x, then

4x × x = 196

or, $4x^2$ = 196

or, x = 7

Thus, Father's age = 28 yrs,

Son's age = 7 yrs

After 5 yrs, Father's age = 33 yrs.

Son's age = 12 yrs

∴ Ratio = 33 : 12 = 11 : 4

Answer: (c)

Total age of the family of five members

= 24 × 5 = 120

Total age of the family of five members before 8 years

= 120 – 5 × 8 = 120 – 40 = 80

So, Required average age = $80/5$ = 16yr

Answer: (b)

Let the ages of children be

x, (x + 3), (x + 6) and (x + 12) years.

Then, x + (x + 3) + (x + 6) + (x + 9) + (x + 12) = 50

⇔ 5x = 20 ⇔ x = 4.

∴ Age of the youngest child = x = 4 years.