Any methods on solving this

Shadows · #1 $Old$ November 3rd, 2009, 09:22 PM

If each of the 10 digits is chosen at random, how many ways can you choose the following numbers?

A)A two-digit code number repeated digits permitted
B)A Three digit identification card number, for which the first digit cannot be a 0.

If can answer at least one that would be great and thanks.

Grandad · #2 $Old$ November 4th, 2009, 03:37 AM

Hello Shadows

Welcome to Math Help Forum!

Quote:

Originally Posted by Shadows $View Post$

If each of the 10 digits is chosen at random, how many ways can you choose the following numbers?

A)A two-digit code number repeated digits permitted
B)A Three digit identification card number, for which the first digit cannot be a 0.

If can answer at least one that would be great and thanks.

A) There are $10$ ways of choosing the first digit, and $10$ ways of choosing the second digit. So there are $10\times10=100$ ways of choosing the two digits, one after the other. (The codes are, of course, from $00$ to $99$ inclusive.)

B) There are only $9$ choices for the first digit, followed by $10$ for each of the other two digits. So there are $9\times10\times10=900$ possible choices altogether.

Grandad