Answer:
a) 12.5 hours and b) 4 water pumps
Explanation:
a) If 6 wp is filled in 15 hours, then:
5 wp is filled in X hours
X hours = (5*15)/6
X = 12.5 hours.
b) If 6 wp is filled in 15 hours, then:
Ywp is filled in 9 hours
Ywp = (9*6)/15
Ywp = 3.6 aprox 4 water pumps