Math CentralQuandaries & Queries


Question from Kim, a student:

Zack has two spinners with numbers on them. the probability of spinning a 7 on both spinners is 3/20. if the probability of spinning a 7 on the first spinner alone is 1/4 what is the probability of getting a 7 on the second
spinner alone?

Hi Kim,

Since these are two different spinners I think that the result on the second spinner is independent of the result on the second spinner. This means that

Pr(7 on both spinners) = Pr(7 on the first spinner) × Pr(7 on the second spinner)

Can you finish the problem?

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