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Level 1

Some months in a year have 31 days. Some months have 30 days. How many months have 28 days?

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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, interactive explorations.

Used and loved by over 7 million people

Learn from a vibrant community of students and enthusiasts,
including olympiad champions, researchers, and professionals.

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by Johnson Nguyen

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