Question 367854
Timothy can mow his lawn in 40 minutes, but his brother Shamus needs only 30 minutes to mow the same lawn. If they work together on the lawn, how long will it take them to finish mowing?
.
Let x = time (minutes) for both to mow the lawn
then
x(1/40 + 1/30) = 1
Multiplying both sides by (40)(30):
x(30 + 40) = 1200
70x = 1200
x = 1200/70 
x = 17.143 minutes
Or,
x = 17 minutes (approximately)