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Original Question
How many 5-digit even numbers can be made using the digits 2, 4, 6, 7, and 8, if digits cannot be repeated?Asked by Tomas
How many 5-digit odd numbers can be made using the digits 3, 5, 6, 7 and 9, if digits cannot be repeated?
Answers
Answered by
Steve
There are only 4 ways to choose the final digit, since it must be an odd number. After that one is chosen, any unused digits may be selected in the other places. So, selecting the digits right-to-left, there are
4*4*3*2*1 = 96 ways to choose the digits.
4*4*3*2*1 = 96 ways to choose the digits.
Answered by
Tomas
if the digits 1,3,5.7,9, what is the different
Answered by
Steve
if all the digits are odd, then there are 5 choices for the last digit. So, the number of choices changes to
5*4*3*2*1 = 120
was that not immediately clear?
5*4*3*2*1 = 120
was that not immediately clear?
Answered by
Tomas
If digits cannot be repeated,how many three digit numbers can be made using the digits 3, 5, 7 and 9 ?
Answered by
Tomas
I know if four digit using the digit 3,5,7,and 9 , the answer is 4*3*2*1=24,
but if three digit using the digit 3, 5,7, and 9, the answer is 3*2*1=6?
but if three digit using the digit 3, 5,7, and 9, the answer is 3*2*1=6?
Answered by
Steve
no; there are 4 choices for the 1st digit, then 3, then 2, so
4*3*2 = 24
Start with the greatest number of choices and work down. You don't have to end at 1.
A 3-digit number using the digits 1,3,5,7,9 would have 5*4*3 = 60 ways.
4*3*2 = 24
Start with the greatest number of choices and work down. You don't have to end at 1.
A 3-digit number using the digits 1,3,5,7,9 would have 5*4*3 = 60 ways.
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