Monika and Marcelo's family owns two lawnmowers; a riding mower and a push mower. A person using the riding mower can completely mow the family's yard in 45 minutes. A person using the push mower can completely mow the yard in 105 minutes. If Monika uses the riding mower and Marcelo uses the push mower, how many minutes will it take to complete the job working together?
Solve like this:
1/45 + 1/105 = 1/t solve for t = 31.5 min
or this
1 / ( 1/45 + 1/105) = t
or this
(105 * 45)/(105+45) = t