Question

A worker can build a fence in 8 hours, With the help of an assistant, the fence can be built in 5 hours. How long should it take the assistant, working alone, to build the fence?

Answer 1

Wouldn't it be the same amount of hours?

Answer 2

What was wrong with my previous answer?

Answer 3

9 hours.

Answer 4

Not necessarily. And could you please show some work?

Answer 5

well lets say the assistant worked at the same rate as the worker. then it would take half the time, 4 hours right.

Answer 6

Oh. Nevermind. The answer is 40/3 hours.

Answer 7

oh :(

Answer 8

13 hours? how?

Answer 9

Worker=W
Assistant=A

1/A+1/W=1/5

1/A+1/8=1/5

8+A/8A=1/5

5*(8+A)=8A

40+5A=8A

3A=40

A=40/3 hours

Answer 10

are you sure?

Answer 11

why 1/A ?

Answer 12

It's the work rate.

Answer 13

Algebra.

Answer 14

why is the rate 1/A ?

Answer 15

sorry, i dont get it

Answer 16

So it takes you 6 minutes to shower, right?

Answer 17

You've showered for 2 minutes already. Doesn't that mean that you showered for 2/6 of the regular shower time or 1/3?

Answer 18

http://www.purplemath.com/modules/workprob.htm

Answer 19

That makes sense.