1992 AMC 8 Problem 23

Below is the professionally curated solution for Problem 23 of the 1992 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1992 AMC 8 solutions, or check the answer key.

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Concepts:dice (probability)systematic listing

Difficulty rating: 1150

23.

If two dice are tossed, the probability that the product of the numbers showing on the tops of the dice is greater than 1010 is

37\dfrac37

1736\dfrac{17}{36}

12\dfrac12

58\dfrac58

1112\dfrac{11}{12}

Solution:

There are 3636 equally likely outcomes. Counting the ordered pairs whose product exceeds 1010: with a first die of 22 there is 11 (namely 2×62 \times 6); of 33, there are 33; of 44, there are 44; of 55, there are 44; of 66, there are 5.5.

That is 1+3+4+4+5=171 + 3 + 4 + 4 + 5 = 17 favorable outcomes, so the probability is 1736.\dfrac{17}{36}.

Thus, the correct answer is B .

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