human
Tom Sawyer has tricked his friends into whitewashing Aunt Polly's 100-foot fence. His first friend, Ben, whitewashed 10 feet. His second friend Billy whitewashed a fifth of the remaining fence. A third friend, Johnny, whitewashed a third of the fence that was left after that. How much of the fence still needs to be whitewashed?
assistant
How many feet of fence are left after Ben is done? ** It's a 100-foot fence, and Ben whitewashed 10 feet, so there are 100 - 10 = <<100-10=90>>90 feet left after Ben is done.
How many feet of fence did Billy whitewash? ** Billy whitewashed a fifth of that, or 90 / 5 = <<90/5=18>>18 feet.
How many feet of fence are left? ** There is now 90 - 18 = <<90-18=72>>72 feet of fence left.
How many feet of fence does Johnny whitewash? ** Johnny whitewashes a third of that, or 72 / 3 = <<72/3=24>>24 feet.
How many feet of fence are left to be whitewashed? ** That leaves 72 - 24 = <<72-24=48>>48 feet of fence left to be whitewashed.
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