Posted by Madison on Tuesday, August 31, 2010 at 9:32am.
Mike can mow a lawn in 3 hours. Paul can mow the same lawn in 2 hours. How long would it take both of them working together to mow the lawn? The answer is suppose to be 20/9.
This is what I did and I get 9/20. What am i doing wrong?
1.4x+1/5x=1 which gives u 9/20. I'm so lost...

Math  Reiny, Tuesday, August 31, 2010 at 9:36am
Mike's rate = 1/3 lawn/hr
Paul's rate = 1/2 lawn/h
combined rate = (1/3 + 1/2) lawn/hr
= 5/6 lawn/hr
time for combined rate = 1/(5/6) hours
= 6/5 hours
Their answer is wrong.
How can it take 20/9 or more than 2 hours for both of them to do it, when Paul alone could do it in 2 hours.

Math  Bob, Saturday, October 16, 2010 at 8:11pm
6/5hrs

Math  Henry, Monday, December 27, 2010 at 6:36pm
t = 3*2 / (3+2) = 6/5 hrs.
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