Answer:
15
Step-by-step explanation:
Let x represent the number of hours it takes the larger hose to fill the pool. Then each hour, it contributes 1/x of the pool volume. Similarly, the other hose contributes a volume of 1/(1.5x) each hour.
The two hoses together contribute a volume of 1/9 of the pool volume each hour:
1/x +1/(1.5x) = 1/9
2.5/(1.5x) = 1/9 . . . . combine the fractions
22.5/1.5 = x . . . . . . multiply by 9x
15 = x
It takes the larger hose 15 hours to fill the pool alone.
