Correct Answer - Option 3 : 36 days
Given:
A works twice as fast B
Together they finish the work in 12 days
Concept Used:
If a person takes t days to complete a work then in 1 day he will do 1/t part of the work
Calculation:
Let be A take X days to complete the work.
Then B takes 2X days to complete the work.
A’s 1 day’s work ⇒ 1\X
B ‘s1 day’s work ⇒ 1\2X
A and B take 12 days to complete the work.
Net work done by (A + B) in 1 day
⇒ 1/12 = 1/x + 1/2x
⇒ 1/12 = 3/2x
⇒ 2X = 36
⇒ X = 18
B can complete the work by himself in 36 days.
∴B will take 36 days.
