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February 28, 2015

February 28, 2015

Posted by **Ann** on Wednesday, January 5, 2011 at 9:44pm.

How many odd four-digit numbers, all of the digit different can be formed from the digits 0 to 7, if there must be a 4 in the number?

- Math (Reiny) -
**Reiny**, Wednesday, January 5, 2011 at 10:40pmAnn, you are right,

I read the question rather superficially and did not fully register that the zero was included, and we had 8 digits instead of 7

I will also assume that a 4-digit number would not start with a 0.

so lets look at those 3 cases again.

case 1: starts with a 4 and ends with an odd, placing the odd digits in 4 ways in the 4th place.

1x6x5x4 = 120

case 1: the "4" is in the second position, but that means we cannot start with a 0

5x1x5x4 = 100 , the zero could go in the 3rd place

case 3: same as case 2 , 5x5x1x4

= 100

total = 120+100+100 = 320

This is is reference to question

http://www.jiskha.com/display.cgi?id=1294266559

- Math (Reiny) -
**Ann**, Wednesday, January 5, 2011 at 11:03pmReiny,

Thank you so very much!!!

- Math (Reiny) -
**Reiny**, Wednesday, January 5, 2011 at 11:07pmYou are welcome, sorry about the error.

Good for you to catch it.

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