Math CentralQuandaries & Queries


Question from Marcus:

If i have 42 numbers to choose from and i could only choose 6 numbers at a time without choosing the same number twice in the same row, how many possibilities are there?

Hi Marcus,

The number of ways of choosing 6 objects from 42 objects is called 42 choose 6 and is written by mathematicians as 42 choose 6but sometimes you see it designated 42C6. The definition is

n choose k

where k! = k × (k-1) × (k-2) × (k-3) × ··· × 1. (For example 5! = 5 × 4 × 3 × 2 × 1 = 120.) Thus

n choose k

After some simplification this becomes

n choose k

I'll let you do the arithmetic.


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