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| Math Central | Quandaries & Queries |
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Question from Megon, a parent: Of the 24 four-digit numbers formed from the digits 1,2,3,&4 is there an easier way to find their sum other than writing them all out and totaling them by hand? |
Hi Megon.
Sure. Total up the units digits. Each of the four digits 1, 2, 3 and 4 appears six times, so adding the units digits is equivalent to
6(1) + 6(2) + 6(3) + 6(4) = 6(10) = 60.
If the units digits add to 60, then what about the 10's digit and so on?
Hope this helps,
Stephen La Rocque.
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