<PRE><B>Question 291155</B>
it takes Steve 3 hours to mow the lawn and Shannon 4 hours to mow the same lawn. How long would it take them to mow the lawn together?

{{{ 1/(1/3 + 1/4) }}}
{{{ 1/(4/12 + 3/12) }}}
{{{ 1/(7/12) }}}
12/7 or 1 5/7 or approx 1.7 hours
would make sense for them to take less than 3 hours

1 job per 3 hours = 1/3 jobs per hour
1 job per 4 hours = 1/4 jobs per hour
add and take reciprocal to find how long it takes to mow together
which is about 1.7 hours
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