a mother takes 64 minutes to mow a lawn when she works along

a mother takes 64 minutes to mow a lawn when she works along using a gas mower. her daughter takes three times as long using a reel mower. how long would it take them to mow the lawn together?

Solution

64(3*64)/64+(3*64)
64*192/(64+192)
12,288/256=48 minutes to mow the lawn when they work together.