2020 AMC 8 Problem 7
Below is the video solution and professionally curated solution for Problem 7 of the 2020 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2020 AMC 8 solutions, or check the answer key.
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Difficulty rating: 1020
7.
How many integers between and have four distinct digits arranged in increasing order? (For example, is one integer.)
Video solution:
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Written solution:
The thousands digit must be Since the digits are distinct and increasing, the hundreds digit must be
The last two digits must be chosen from Once the two digits are chosen, their order is forced.
There are such integers.
Thus, the correct answer is C.
Problem 7 in Other Years
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