<human>:  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?
<bot>: How long does it take Janet to cross the lake? ** First find how long it takes Janet to cross the lake: 60 miles / 30 miles/hour = <<60/30=2>>2 hours
How long does it take her sister to cross the lake? ** Then find how long it takes her sister to cross the lake: 60 miles / 12 miles/hour = <<60/12=5>>5 hours
How long does it take her sister to catch up? ** 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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