Question

A and B can do a piece of work in 6 and 12 days, respectively. They (both) will complete the work in how many days?

Options

• 9 days

• 18 days

• 6 days

• 4 days

Answer 1

4 days

Explanation:

A's 1 day's work = `1/6`

B's 1 day's work = `1/12`

(A+ B)'s 1 day's work = `1/6+1/12`

= `(2+1)/12=3/12=1/4`

Hence, both will complete the work in 4 days.

Second Method

Here, x = 6

and y = 12

∴ Time taken by (A+ B) = `(xy)/(x+y)`

= `(6xx12)/(12+6)` = 4 days