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. 
<pre>
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/M + 1/3 = 1/1}}}
{{{1/M + 1/3 = 1}}}
3 + M = 3M ------ Multiplying by LCD, 3M
3 = 3M - M
2M = 3
M, or time Mark takes, alone, to mow = {{{3/2}}}, or {{{1&1/2}}} hours
Mark's rate: {{{1/M}}}, or {{{1/(3/2)}}}, or {{{highlight_green(highlight_green(2/3))}}} of lawn in 1 hour