Answer: 810
<u>Step-by-step explanation:</u>
There are 10 numbers to choose from. Since the 2nd digit and 3rd digit cannot repeat the number before it, they only have 9 numbers to choose from.
1st digit and 2nd digit and 3rd digit
10 choices x 9 choices x 9 choices = 810
Answer:
169
Step-by-step explanation:

It is rational because it is a terminating decimal. It can be represented as a ratio of two integers (121/10)