Question

Item 19 Your pump empties the water from a swimming pool in 6 hours. When your friend's pump is used together with your pump, the pool is emptied in 1.5 hours. How long (in hours) does it take your friend's pump to empty the pool when working alone

Answer 1

0.75 hours

Explanation:

Time taken by my pump = 6 hours

Time taken by friend's pump = x

Combined time = 1.5 hours

Rate :

my pump = 1/6

Combined rate = 1/1.5

Combinwd rate = 1/6 + 1/x

Hence :

1/6 + 1/x = 1/1.5

(x + 6) / 6x = 1.5

x + 6 = 9x

x - 9x = - 6

-8x = - 6

x = - 6 / - 8

x = 0.75 hours