Question

9.
A and B together can finish a piece of work in 12 days. If'A' alone can finish the same
work in 20days, in how many days B alone can finish it?
​

Answer 1

Answer:

30 days

work done by A and B in 1 day = 1/12

worl done by A in one day = 1/20

therefore work done by B in 1 day =1/12 - 1/20

=2/60

hence B alone can complete the work in 60/2 dsys =30days

Answer 2

Step-by-step explanation:

Time taken by A and B together = 12 days

Work done by A and B together in 1 day= 1/12unit

Time taken by A alone = 20 days

Work done by A alone in 1 day= 1/20 unit

Work done by A alone in 1 day =

(Work done by A and B together in 1 day)

- (Work done by A alone in 1 day)

$= \frac{1}{12} - \frac{1}{20} \\ = \frac{5}{60} - \frac{3}{60} \\ = \frac{2}{60}\\ =\frac{1}{30}$

Time taken by B alone

$= \frac{1}{ \frac{1}{30} } \\ = 30$

B alone can finish it in 30 days.