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jmc

prealgebra senior

Problem

Spinner I is divided into four equal sections labeled 2, 3, 4 and 5. Spinner II is divided into five equal sections labeled 1, 3, 5, 7 and 9. If each spinner is spun and the resulting numbers are multiplied, what is the probability that the product is a two-digit even number? Express your answer as a common fraction.
Solution
Let results be denoted by ordered pairs where the first coordinate corresponds to Spinner I and the second coordinate corresponds to Spinner II. Since all the section numbers on Spinner II are odd, Spinner I must given an even number in order for the product to be even. The results , , , , , , and are the ones whose products are two-digit even numbers. Since there are equally likely results, the probability of obtaining an even two-digit product is .
Final answer
\frac{7}{20}