Question 424136
Jack mows his lawn in six hours, Mary takes seven hours to mow the lawn.
 If they work together how long would it take them?
:
Let t = time required if they both mow; (and each has a lawn mower)
Let the completed job = 1 (a mowed lawn)
:
{{{t/6}}} = {{{t/7}}} = 1
multiply by 42, to clear the denominators, results:
7t + 6t = 42
13t = 42
 t = {{{42/13}}}
t = 3.23 hrs, or 3 + .23(60) ~ 3 hrs 14 min
:
:
Check solution
{{{3.23/6}}} = {{{3.23/7}}} =
.54 + .46 = 1; confirms our solution of t = 3.23 hrs