Lisa can shovel her driveway in 30 minutes and Tom can shovel his driveway in 40 minutes. How long will it take them to shovel the driveway together?

Answer 1

how much work is done each hour?

1/30 + 1/40 = 1/x

It will take them x hours working together.

Actually, the problem is very poorly worded, since the times are for shoveling their own driveways, and we have no idea which driveway they work on together.