Question

1. Jennifer can mow the lawn in 20 min. Kristen can mow the lawn in 30 min. If they work together, how long will it take them to mow the lawn

Answer 1

Sam can do the job in 20 min. So he can do the whole job at the rate of 1 job in 20 minutes.

So he does 1/20 of the job per minute.

.

Rob can do the job in 30 min. His rate is 1/30 of the job per minute.

.

Working together how does it take?

.

1/20*x + 1/30*x = 1 job done

, where x = minutes.

.

Explanation: