SOLUTION: Mary and Chris, together can clean their house in 2 hours. Mary alone can clean the house in 3 hours and 30 minutes. How long does it take Chris to clean the house working alone?

Question 180966This question is from textbook College Algebra
: Mary and Chris, together can clean their house in 2 hours. Mary alone can clean the house in 3 hours and 30 minutes. How long does it take Chris to clean the house working alone? This question is from textbook College Algebra

Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Let x=amount of time it takes Chris working alone to clean the house
Chris therefore works at the rate of 1/x house per hour
Mary and Chris working together works at the rate of 1/2 house per hour
Mary alone works at the rate of 1/(3.5) house per hour
Now we are told that:
1/x + 1/(3.5)=1/2 multiply each term by 7x
7+2x=3.5x subtract 2x from each side
7=3.5x-2x
1.5x=7
x=4 2/3 hours------------------amount of time it takes Chris working alone
4 2/3=14/3
3 1/2=7/2
3/14 +2/7=1/2
3/14+4/14=1/2
1/2=1/2
Hope this helps---ptaylor
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