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Medium combinatorics

Discrete Mathematics Level 2

Let's crank up the level!

How many three digit numbers are there such that the first digit is bigger than the last one?

Excel in math and science

Master concepts by solving fun, challenging problems.

It's hard to learn from lectures and videos

Learn more effectively through short, conceptual quizzes.

Our wiki is made for math and science

Master advanced concepts through explanations,
examples, and problems from the community.

Used and loved by 4 million people

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including olympiad champions, researchers, and professionals.

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by Eric Hernandez

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