2024 AMC 8 Problem 5

Attempt Problem 5 of the 2024 AMC 8 below, then check your answer against the video solution and professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2024 AMC 8 solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

5.

Aaliyah rolls two standard 6-sided dice. She notices that the product of the two numbers rolled is a multiple of 6. Which of the following integers cannot be the sum of the two numbers?

55

66

77

88

99

Answer: B
Concepts:dice (probability)divisibilitycasework
Difficulty rating: 960
Video solution:
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Written solution:

For the product to be a multiple of 66, the two dice together must supply a factor of 22 and a factor of 33. The possible sums among the answer choices can occur as follows: 5=2+3,7=1+6,8=2+6,9=3+6. \begin{gathered} 5=2+3,\quad 7=1+6, \\ 8=2+6,\quad 9=3+6. \end{gathered} There is no way to get sum 66 while also having a product divisible by 66: the pairs with sum 66 are (1,5),(2,4),(3,3),(4,2),(5,1)(1,5),(2,4),(3,3),(4,2),(5,1), and none have product divisible by 66.

Thus, B is the correct answer.

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