Question 891983
Gregory can mow the family's lawn in 3 hours, and Jennifer can mow it in 4 hours.
 If they team up to mow the lawn together, how long will it take to finish mowing the lawn?
:
let x = time required when mowing together (two lawn mowers, obviously)
;
Let the completed job = 1 (a mowed lawn)
:
Each will do a fraction of the lawn, the two fractions add up to
:
{{{x/3}}} + {{{x/4}}} = 1
Multiply the equation thru by 12, cancel the denominators and you have:
4x + 3x = 12
7x = 12
x = 12/7
x = 1.71 hrs or 1 + .71(60) = 1 hr 43 min