Problem:
Every time these two wheels are spun, two numbers are selected by the pointers. What is the probability that the sum of the two selected numbers is even?
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Answer Choices:
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Solution:
The set of all the possible outcomes of spinning each wheel is
There are six even sums among the outcomes for a probability of .
Consider the outcome on the right wheel first. Whatever number occurs, there are two out of four chances for the number on the left wheel to give an even sum. Thus the desired probability is .
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions