Question

A and B together can do a piece of work in 15 days. But A alone can do it in 20

days. How many days would B take alone to do the same work?​

Answer 1

Answer:

5 days is the correct answer.....

Answer 2

This problem can be solved hell lot of ways :-)

Lets solve the problem by intuitively…

Here first thing is, the work is same irrespective of how many members going to complete. Isn’t it?

let’s say entire work is done means he/she has done 100% of the work.

Reasonably, according to the statement,A alone can complete only 5% of the work per day. (100/20=5)

A +B worked for 15 days→ A completed 15*5=75% of the work . Thus , rest 25% work has been completed by B in 15 days.

B has done 25% of the work in 15 days. Thus, he would take 60 days to complete the whole work. (15 *4=60)

Second way:

If you are really good at maths: It is a simple equation.First consider 1 day of work.

A→1/20

B→ Don’t know

A+B=1/15.

Thus, 1/20+1/B=1/15. If you solve this B would get 60. ( you need to be very strong in maths by watching the equation to find out 60 for B).

So in one day B would complete 1/60th work . To complete entire work he would take 60 days.