Final answer:
Joe and Jerry can mow the lawn in 18 minutes if they work together. Joe mows the lawn at a rate of 1/45 per minute, and Jerry at 1/30 per minute. Their combined rate is 1/18 of the lawn per minute.
Step-by-step explanation:
The question pertains to the rate at which two people can complete a task together. To solve this, we find the rate at which each person works and then combine these to find their combined rate.
Joe takes 45 minutes to mow the lawn, which means he can mow 1/45 of the lawn per minute. Jerry mows the lawn in 30 minutes, so his rate is 1/30 of the lawn per minute. To find out how long it will take them to mow the lawn together, we add their rates:
Joe's rate: 1/45 lawn per minute
Jerry's rate: 1/30 lawn per minute
Combined rate: 1/45 + 1/30 = 2/90 + 3/90 = 5/90 = 1/18 lawn per minute
Therefore, to mow the entire lawn, it would take them 1/(1/18) minutes or simply 18 minutes.