remainder finding?

2 ⤊

whats the remainder when 21!-4! divided by 64 ?

2007-07-04 06:07:25 · 3 answers · asked by sanko 1 in Science & Mathematics ➔ Mathematics

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please explain answer

2007-07-04 06:20:01 · update #1

3 answers

Let's work mod 64.
Note that 21! is divisible by 8 and 16,
both of which have 8 as a factor,
so 21! = 0(mod 64).
So 21! -4! = -4! = -24(mod 64),
and -24 = 40(mod 64).

2007-07-04 07:39:57 · answer #1 · answered by steiner1745 7 · 0⤊ 0⤋

2007-07-04 13:12:51 · answer #2 · answered by oregfiu 7 · 1⤊ 0⤋

(21! - 4!) mod 64 = 40

2007-07-04 14:01:01 · answer #3 · answered by ? 5 · 1⤊ 0⤋