# Work Problem

• Oct 27th 2008, 10:16 PM
magentarita
Work Problem
Barn Painting. Melanie can paint a certain barn by herself in x days. Her helper Melissa can paint the same barn by herself in 2x days. Write a rational expression for the fractions of the barn that they complete in one day by working together. Evaluate the expression for x = 5.

I came up with this:

Melanie = 1/x

Melissa = 1/2x

Together = 1/x

1/x + 1/2x = 1/x

What is the right set up?

I can evaluate when x= 5. I just need the proper rational expression.

Thanks

• Oct 28th 2008, 05:21 AM
HallsofIvy
Quote:

Originally Posted by magentarita
Barn Painting. Melanie can paint a certain barn by herself in x days. Her helper Melissa can paint the same barn by herself in 2x days. Write a rational expression for the fractions of the barn that they complete in one day by working together. Evaluate the expression for x = 5.

I came up with this:

Melanie = 1/x

Melissa = 1/2x

Together = 1/x

??? Do you realize that you are saying that, working together, they work no faster than when Melanie works by herself? There is no "equation" here- you just want to add the two rates together to find how fast they work together. What is 1/x+ 1/2x ?

And another thing- don't just write "Melanie= 1/x". The girl is not a number. Write "the rate at which Melanie paints the barn = 1/x". That makes it clear exactly what that number represents.

Quote:

1/x + 1/2x = 1/x

What is the right set up?

I can evaluate when x= 5. I just need the proper rational expression.

Thanks

• Oct 29th 2008, 08:43 AM
magentarita
Can you....
Quote:

Originally Posted by HallsofIvy
??? Do you realize that you are saying that, working together, they work no faster than when Melanie works by herself? There is no "equation" here- you just want to add the two rates together to find how fast they work together. What is 1/x+ 1/2x ?

And another thing- don't just write "Melanie= 1/x". The girl is not a number. Write "the rate at which Melanie paints the barn = 1/x". That makes it clear exactly what that number represents.

1/x + 1/2x = 3/2x

If I then let x = 5, this is what I get:

3/(2(5)) = 3/10 = 3/10

What does 3/10 mean in this case?

Is this correct?