At its simplest, probability can be defined as The number of favorable outcomes divided by the number of total outcomes. We will be using this formula throughout the quarter, especially in the context of proportions.
For instance, suppose that you randomly select a whole number at least 0 and at most 99 (that is, one of 0,1 , $2, \ldots, 99)$ from a sequence of random numbers obtained by repeatedly spinning a spinner. What is the probability that the number selected
a) is greater than 80 ?
b) is a multiple of 3 ?
(Hint: Zero is also a multiple of three.)

Step 1 ：Define probability as the number of favorable outcomes divided by the number of total outcomes.

Step 2 ：Consider a sequence of random numbers obtained by repeatedly spinning a spinner, where you randomly select a whole number at least 0 and at most 99.

Step 3 ：For part a), the favorable outcomes are the numbers greater than 80, which are 81 to 99. There are 19 such numbers. The total outcomes are the numbers from 0 to 99, which are 100 in total. So the probability is the number of favorable outcomes divided by the number of total outcomes, which is \(\frac{19}{100}\).

Step 4 ：For part b), the favorable outcomes are the multiples of 3, which are 0, 3, 6, ..., 99. To find out how many such numbers there are, we can divide the largest multiple of 3 within the range, which is 99, by 3, and add 1 (because we start counting from 0). So there are 34 such numbers. The total outcomes are the same as in part a), which are 100. So the probability is the number of favorable outcomes divided by the number of total outcomes, which is \(\frac{34}{100}\).

Step 5 ：Final Answer: The probability that the number selected is greater than 80 is \(\boxed{0.19}\) and the probability that the number selected is a multiple of 3 is \(\boxed{0.34}\).