1!+2!+3!+4!+.....+100! is devided by 15 ? and how to calculate it ?
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Hello, You can notice that 15=3x5 This means that for all n > (or equal) 5, n! will contain 15 in its factors. So we know that (5!+6!+...+100!) is a multiple of 15. 1!+2!+3!+4!=1+2+6+24=33 --> the remainder is 3.
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