How many odd five-digit counting numbers can be formed by choosing digits from the set [1,2,3,4,5,6,7] if digits can be repeated?

CalTheGreat Mar 22, 2020

#1**+3 **

The 5 digit number will end in either 1, 3, 5 or 7

Since digits can be repeated we have 7 choices for each of the 4 leading positions and 4 choices for the ending digit

So....the total number of odd five-digit countig numbers =

7^4 * 4 =

9604

CPhill Mar 22, 2020

#2**+3 **

A different perspective...just an FYI

7^{5 }possible numbers 4 out of 7 are odd 7^{5} x 4/7 = 9604 (as Chris calculated)

ElectricPavlov Mar 22, 2020

#3

#4**0 **

Cal has told me that this wasn't actually her question.

The system is sometimes capturing her username and assigning it to guest questions that have just been posted.

I assume she is on shared wifi or something like that.

Anyway she says she is glad it happened this time because she learned a lot from EP and Chris who so kindly answered this question.

Thanks guys

**It is so nice to know that we have genuine learners here. Thanks Cal. **

Melody
Mar 24, 2020