Aptitude - Time and Work - Discussion

Elaborate how you do this (1/50+1/20) where did you get 1/50?

In how many days A & B together complete the same job?

Thank you, everyone those have written explanation here. It really helps.

Why you subtract 7/15 from 1?

For those who have difficulty with fractions, here is an alternative.

Let the total work be to lay 120 bricks. (I chose 120 as it can be divided easily by both 15 and 20).

Takes 15 days to lay 120 bricks, That means in one day he can lay 8 bricks.

B takes 20 days to lay 120 bricks. That means B can lay only 6 bricks in one day.

Together they can lay 8+6=14 bricks.

Therefore, in 4 days, they will lay 14*4= 56 bricks only.

Remaining bricks to be layed is 120-56=64 bricks.

That means, 64/120=8/15 of the work is remaining.

Fraction of work done in 4 days = 7/15.
(It means that out of 15 parts, 7 parts has been done. So 8 parts left)

Therefore, the fraction of work left = 8/15.

Work is 1part. A and B work is finished 7/15 part in 4days from 1part. Remaining work is 1 - 7/15 = 8/15.

I'm confused with this step (1 - 7/15). Can anyone explain this?

Harry is correct.

Hi @Deepa, leave that 1-7/15 & %method, simply total efficiency is 7/day, no of worked together is 4, then multiply it becomes 28.

Subtract from total work done 60 - 28 = 32. To find the answer for ques-> 32/60 = 8/15. Cool.

I'm confused with this stem (1 - 7/15). Can anyone explain this?