a fill pipe can fill 2 / 3 of cistern in 40 minutes in how many minutes , it can fill full of the cistern ?
2 / 3 of the cistern can fill in 40 min 3 / 3 of the cistern can fill in = 40 * 3 / 2 * 3 / 3 = 60 min answer is a
divide(40, divide(2, 3))