Question

A and b completed a work in 5 days. Had a worked at twice the speed of b and b as half the speed of a, it would have taken them 4 days to complete the job. How much time would it take for a alone to do the work?

Answer 1

let the speed of a and b are x and y respectively
let the total work =A so, A/5

A=5x+5y
next a speed double b speed half so, take 4days
2x+y/2=A/4
A=8x+2y
so, 8x+2y=5x+5y
3x=3y
x=y
that's why 2x complete in 5days
x complete in 10days