Question

A 500m long railway track is being repaired.At the end of the 3 days, the workers had repaired 3/4 of the railway track.what length of the railway track is left unrepaired?

Answer 1

Total length = 500m
Work Done after 3 days = 3/4 × 500
=375
So Work left to do = (500 - 375)m
= 125m

So 125m of the railway track is still left unrepaired!

Answer 2

let x days be time required for complete work to be done
therefore in 1 day 1/x work is done.....A
3 days takes 3/4 work
therefore 1 day 1/4 work is done.....B
equate A and B
hence x = 4days
so if 3 days are over, 1 day is remaining
therefore 1/4 work is left
so 1/4 of 500m is 125m
hence 125m of railway track is left to repair

you can compact this answer but I have written it so that you can understand