2020 AMC 10A Problem 6

Attempt Problem 6 of the 2020 AMC 10A 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 2020 AMC 10A solutions, or check the answer key.

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6.

How many 44-digit positive integers (that is, integers between 10001000 and 9999,9999, inclusive) having only even digits are divisible by 5?5?

8080

100100

125125

200200

500500

Answer: B
Concepts:multiplication principledigitsdivisibility
Difficulty rating: 980
Video solution:
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Written solution:

The last digit must be 00, because the number is divisible by 55 and all digits are even. The thousands digit can be 2,4,6,2,4,6, or 88, and each of the hundreds and tens digits has 55 choices. Thus there are 455=1004\cdot5\cdot5=100 such integers. Thus, B is the correct answer.

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