Re: Help - simple algebra

On Thu, 20 Mar 2008 22:58:54 GMT, Martin
<martin.wilkins50@[EMAIL PROTECTED]
> wrote in
<news:O_BEj.14454$jH5.8429@[EMAIL PROTECTED]
> in
alt.algebra.help:

> How do you solve this problem

> If Sally can paint a house in 4 hours, and John can paint
> the same house  in 6 hour, how long will it take for both
> of them to paint the house  together?

> 	2 hours and 24 minutes
> 	3 hours and 12 minutes
> 	3 hours and 44 minutes
> 	4 hours and 10 minutes
> 	4 hours and 33 minutes

> Apparently it's 2 hours and 24 minutes

In one hour Sally paints 1/4 of the house, and John paints
1/6 of the house, so between them they can paint 1/4 + 1/6 =
5/12 of the house in an hour.  To paint the whole house will
therefore take them 1/(5/12) = 12/5 hours, or 2 hr. 24 min.

Brian