Question

A man and a boy can complete a work in 20 days. Their skills of doing work is in the ratio of 4 : 1 respectively. How many days will be taken by the boy to do the same work alone?
1. 120
2. 100
3. 10
4. 50

Answer 1

Correct Answer - Option 2 : 100

GIVEN:

A man and a boy can complete a work in 20 days. Their skills of doing work is in the ratio of 4 : 1 respectively.

CONCEPT:

Efficiency and time are inversely proportional.

CALCULATION:

Efficiency ratio = 4 : 1

Suppose the time taken by the man and the boy are x and 4x respectively

So,

1/x + 1/4x = 1/20

⇒ 5/4x = 1/20

⇒ x = 25

A boy will take 4 × 25 = 100 days to complete same work.