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77*7=497*7*7=3437*7*7*7=24017*7*7*7*7=168077*7*7*7*7*7=1176497*7*7*7*7*7*7=8235437*7*7*7*7*7*7*7=5764801由此可見,n個7相乘,它的尾數有規律.每隔4個重複.97/4=24餘1所以97個7的積位數是7再加2,尾數是9.所以÷5…
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