Aptitude - Time and Work - Discussion

^^ We do 20*16 & 16*15 because of the below logic:

It's given that 20W can do the work in 16 days. Going by this, 1W would be able to do the work in 16*20 days. Similarly, for one man, the work can be completed in 15*16 days. But then to find the capacity, you have to take the inverse, it's just like speed & time relation (the ratio of speed & time are reverse).

Hence, we write it as,
M:W = 1/240 : 1/320 = 1/3:1/4 = 4:3

@Dinesh: I feel if the fraction form is given a one of the answers then even that can be marked as the correct answer. But it's common practice to convert any answer into the simplest form & a fraction's not that.

Why we multiply 20*16 and 16*15. Means what is the logic behind it?

Ok what you saying is 100% right Jananipriya. Then why we have to do cross multiple work as they given in last step.

Since the ratio has been asked between man and woman which is 1/240, 1/320 per day respectively. That is it Pavan.

Why we take 1/240:1/320?

Why not 1/320:1/240?

It will give us reverse answer as 3:4 which is the 1st option.

Though here there is no error but there is a shortcut:

The method is as follows

20w -> 16d
16m -> 15d

w:m=20:16=4:5 i.e., according to number of w and m
w:m=16:15 i.e., according to num of days they take

Then the ratio between m amd w according to their capacity will be
= (16:15 :: 4:5)
= 16/4 : 15/3
= 4:3

This could be done because the ratio of capacity is always reverse of number of days taken.

Thanks Sheetal, it is very understandable solution.

Sheetal your explanation is too good.

Thank you.

Thank you Sheetal!