SOLUTION: Hello, I am taking some practice test for the College placement test and I am having difficulty solving a problem. This is Alegebra 1. I just need to know how to solve the probl

Question 6835: Hello,
I am taking some practice test for the College placement test and I am having difficulty solving a problem. This is Alegebra 1. I just need to know how to solve the problem. Thank you in advance. I only put the answers so you can see my options.
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?

A. 2 hours and 24 minutes
B. 3 hours and 12 minutes
C. 3 hours and 44 minutes
D. 4 hours and 10 minutes
E. 4 hours and 33 minutes

Answer by longjonsilver(2297) (Show Source):
You can put this solution on YOUR website!
sally paints a house in 4 hours --> in 1 hour she paints 1/4 of house
john paints a house in 6 hourse --> in 1 hour, he paints 1/6 of house.

So, in 1 hour together they will paint 1/4+1/6 of the house ie

they paint 5/12 of house in 1 hour. So divide by 5/12, and we get:
(5/12)/(5/12) in 1/(5/12) hours
--> they paint 1 whole house in 12/5 hours.

this is 2.4 hours, ie 2 hours 24 minutes.

jon.