Question 414687
a watertank empty in 42 seconds from 1st hole and empty in 30 seconds from the 2nd hole.in how many time the watertank will be empty when both holes are opened
.
Let x = time (seconds) for both holes to empty tank
then
x(1/42 + 1/30) = 1
multiply both sides by (42)(30)
x(30 + 42) = (42)(30)
x(72) = (42)(30)
x = (42)(30)/(72)
x = 17.5 seconds