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What Does This C Symbol Mean?

Maya Lin-Takahashi • • 1 min read
What Does This C Symbol Mean?
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Problem from China Olympiad

What does the capital C symbol mean?

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1 Answer

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It is the binomial coefficient. There are 3 ways to write it in China:

  • In mainland, we prefer $$C_n^r=\frac{n!}{r!(n-r)!}.$$

  • In Hong Kong, we prefer $$nCr=C_r^n=\frac{n!}{r!(n-r)!}.$$

All are acceptable.

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Maya Lin-Takahashi
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Maya Lin-Takahashi

Maya is a hardware enthusiast who tests and reviews smart home devices, smartphones, wearables, and audio gear. She focuses on practical consumer value and build quality.