Reggie has enough flour to last for 40 days. If he increases his use of flour by 25%, however, how many days’ worth of flour will he have?

Reggie has enough flour to last for 40 days. If he increases his use of flour by 25%, however, how many days’ worth of flour will he have?
A . 30 days
B . 28 days
C . 32 days
D . 48 days
E . 36 days

Answer: C

Explanation:

Reggie will be using flour at 5/4 the normal rate. Since the amount of flour used is inversely proportional to the amount of time it takes to go through the flour, the duration can be found by multiplying 40 by the inverse of 5/4, or 4/5.