Math word problem.

Question

Page


A new type of pump can drain a certain pool in
6

hours. An older pump can drain the pool in
12

hours. How long will it take both pumps working together to drain the pool?

Do not do any rounding.

Answer 1

Let x = number of hours it takes to drain the pool if both pumps are working

 

1/6 = portion drained by the first pump per hour

1/12 = portion drained by the other pump per hour

1/x = portion drained by both pumps per hour

 

1/6 + 1/12 = 1/x

 

Multiply by the LCD, 12x, to obtain 2x + x = 12

 

                                                         3x = 12

 

                                                           x = 4 hours