Answer:
a) 90
b) 100
Step-by-step explanation:
This is a probability problem. In order to solve it, we must multiply the number of possible numbers by eachother.
a) the first digit can be any number between 0 and 9. That's 10 options. The second digit must be different from the first one: that's 9 options. 10x9=90
b) the first digit can be any number between 0 and 9. That's 10 options. The second digit can also be any number between 0 and 9. That's also 10 options. 10x10=100
