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Problem 142

Number theory Difficulty 1.4 Multiple choice CEMC Cayley · Canada · 2024

Two standard six-sided dice are rolled. What is the probability
that the product of the two numbers rolled is 1212?

Pick one

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Official solution

When two standard six-sided dice are rolled, there are 6×6=366 \times 6 = 36 possibilities for the
pair of numbers that are rolled.

Of these, the pairs 2×62 \times 6,
3×43\times 4, 4×34\times 3, and 6×26 \times 2 each give 1212. (If one of the numbers rolled is
11 or 55, the product cannot be 1212.)

Since there are 44 pairs of possible
rolls whose product is 1212, the
probability that the product is 1212
is 436\frac{4}{36}.

Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.