Answer:
.
Step-by-step explanation:
We are told that a spinner has equal regions numbered 1 through 21.
We can see that our both events are not mutually exclusive events, so will use formula to find our desired probability.
= Probability of event A or event B.
= Probability of event A.
= Probability of event B.
= Probability of event A and event B.
Let us find probability that spinner will stop on an even number. Even numbers on spinner's region are: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20.
Now let us find probability that spinner will stop on a multiple of 3. Multiples of 3 on the spinner's region are: 3,6,9,12,15,18,21.
Now we have to figure out probability that spinner will stop on an even number and multiple of 3. Both events happening at one time are: 6,12,18.
Now let us substitute our values in above mentioned formula.
Therefore, probability that the spinner will stop on an even number or a multiple of 3 is .