Janet starts driving across a lake in a speedboat going 30 miles per hour. Her sister follows in a sailboat that has a speed of 12 miles per hour. If the lake is 60 miles wide, how long does Janet have to wait on the other side for her sister to catch up?
First find how long it takes Janet to cross the lake: 60 miles / 30 miles/hour = <<60/30=2>>2 hours
Then find how long it takes her sister to cross the lake: 60 miles / 12 miles/hour = <<60/12=5>>5 hours
Then subtract Janet's travel time from her sister's travel time to find the difference: 5 hours - 2 hours = <<5-2=3>>3 hours
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