2007-03-27 21:09:41 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
3125 combinations 5x5x5x5x5, and the last one has to be correct so 3124
2007-03-27 21:13:44 · answer #1 · answered by Anonymous · 0⤊ 2⤋
all possibles with repeats is 5^5 giving you 3125 and one wrong is 3124.
However if you can't reuse you do 5!, 5 x 4 x 3 x 2 x 1gives you 120 cuz if you wrote all combos down with each number leading you get 24 combos for each number leading and 24 * 5 is 120. Look at my list below if you copy and pasted the two column to far right you get all 24 with 5 leading and if you repeat you would see the 24 list with each number leading. I hope that helped. They get 72 cuz it seems they assume that 4 numbers are stationary or something. This 120 is correct for all and 1 wrong gives you 119, email me with any questions m_lavallee@cox.net
2007-03-28 06:05:13 · answer #2 · answered by niceguyswthrt 2 · 0⤊ 0⤋
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if you can re-use the digits:
5 x 5 x 5 x 5 x 3 = 625 x 3 = 1875
if you MUST use each digit once, then there
are 3 choices for the last digit {2,4,6}
and 4*3*2*1 choices for the first 4 digits
=>
4*3*2*1 * 3 = 24*3 = 72
different phone numbers meeting the stated conditions.
If ONE of these numbers is "right" and all the others wrong, then subtract "1" to get the number of different "wrong" phone numbers.
1875 - 1 = 1874 ........... OR ......
72 - 1 = 71
2007-03-28 04:12:13 · answer #3 · answered by atheistforthebirthofjesus 6 · 1⤊ 1⤋
Total combinations:
Last digit is 2,4 or 6. For each of these there are 4! ways to arrange the other digits. So....
4!*3=72
Ways to go wrong = 71
2007-03-28 04:15:25 · answer #4 · answered by blighmaster 3 · 2⤊ 0⤋