Gurney can mow the lawn in 3 1/2hours. Moneo can mow the lawn in 4 1/4 hours. How long will it take them to mow the lawn if they work together?
1 /3.5 + 1/4.25 =0.521 [This means that working together, they can finish 0.521 of the job in 1 hour]
So, to finish the whole job, we take the reciprocal of that, or:
T =1 / 0.521 =1.919 hours, or ~ 1 hour and 55 minutes.