How long will it take them to mow the lwn

Question

the smith children are responsible for mowing the lawn. if it takes anna 18 minutes and bill 36 minutes, assuming that they have two lawn mowers how long will it takes them to mow the lawn working together

Answer 1

1/Job 1 + 1/Job 2 = 1/Together

Let x = Time for them to mow together

1/18 +1/36 = 1/x

2/36+1/36 = 1/x

3/36 = 1/x

1/12 = 1/x

x=12

It will take them 12 mins to mow the lawn together.