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? Think carefully first, then make a decision:
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It's a 100 - foot fence, and Ben whitewashed 10 feet, so there are 100 - 10 = 90 feet left after Ben is done. Billy whitewashed a fifth of that, or 90 / 5 = 18 feet. There is now 90 - 18 = 72 feet of fence left. Johnny whitewashes a third of that, or 72 / 3 = 24 feet. That leaves 72 - 24 = 48 feet of fence left to be whitewashed. So, the answer is 48.
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