The answer is what is shown on the phone
let the time taken to be filled by both pipes be y
1/2 +1/8=1/y
(4+1)/8=1/y
5/8=y
cross multiplying
5y=8
y=8/5
=1.6hrs
The correct answer would be 16/24. You would need to multiply both the denominator and numerator by 4.
They are both measurements used to measure different distances. Feet are generally used in the US and yards are generally used outside the US. Although you might find yards being used as a unit of measurement in sports like football. Also, feet are usually larger than yards.