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How many ways can the number 30 be written as an ordered sum of 2s and 5s?

  • math -

    15 2's = one way
    10 2's + 2 5's = 12!/(10!2!) ways
    5 2's + 4 5's = 9!/(5!4!) ways
    6 5's = one way
    Total=194

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