Question

A father can do a job in a certain number of hours. His son takes twice as long to do the job. Working together, they can do the job in 6 hours. How many hours does it take the father to do the job alone?

F. 9
G. 10
H. 12.
J. 16
K. 18

Answer 1

Answer is F. = 9 hours

Step by step

Let father = 1/x of the job
Let son = 1/2x of the job

1/x + 1/2x = 6 hours

1/3x = 6

Divide both sides by 1/3 to solve for x

1/3 ÷ 1/3 x = 6 ÷ 1/3
When you divide fractions you flip the divisor fraction and multiply

1/3 * 3/1 x = 6 * 3/1
Simplify

x = 9

So father = 9 hours