SOLUTION: If Lisa and Mark can mow their lawn together in 1 hour, and Lisa can mow the lawn by herself in 3 hours, what is Mark's rate, working alone? I came up with this equation: t1/3 + t

Algebra ->  Rate-of-work-word-problems -> SOLUTION: If Lisa and Mark can mow their lawn together in 1 hour, and Lisa can mow the lawn by herself in 3 hours, what is Mark's rate, working alone? I came up with this equation: t1/3 + t       Log On


   

Question 886951: If Lisa and Mark can mow their lawn together in 1 hour, and Lisa can mow the lawn by herself in 3 hours, what is Mark's rate, working alone? I came up with this equation: t1/3 + t =1 and of course my answer is wrong.

Answer by MathTherapy(10809) About Me  (Show Source):
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If Lisa and Mark can mow their lawn together in 1 hour, and Lisa can mow the lawn by herself in 3 hours, what is Mark's rate, working alone? I came up with this equation: t1/3 + t =1 and of course my answer is wrong. 


Let time Mark takes to mow by himself, be M

Then Mark can mow 1/M of lawn in 1 hour

Lisa can mow lawn in 3 hours, or 1/3 of lawn in 1 hour

Therefore, 1%2FM+%2B+1%2F3+=+1%2F1

1%2FM+%2B+1%2F3+=+1

3 + M = 3M ------ Multiplying by LCD, 3M

3 = 3M - M

2M = 3

M, or time Mark takes, alone, to mow = 3%2F2, or 1%261%2F2 hours

Mark's rate: 1%2FM, or 1%2F%283%2F2%29, or highlight_green%28highlight_green%282%2F3%29%29 of lawn in 1 hour