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| Math Central | Quandaries & Queries |
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What is the tens digit in the sum 7! + 8! + 9! ... + 2006! I know there's an easy way to figure it out but i just can't remember. Thanks |
Hi Emily.
Any of these terms over 10! is a multiply of 10!, right?
And 10! has the factors 10, 5, and 2 (and the others).
What does that tell you?
Cheers,
Stephen La Rocque.
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