question about the math in the tech conference example

Question

The math in they symmetry lesson seems odd to me. Wouldn't it make more sense to write it as this?
10*9*8*7*6*5*4 / 7*6*5*4*3*2*1 = 604,800 / 5040 = 120, which is symmetrical to 720 / 6 = 120

Thanks!
Ryan

Answer 1

Hey Ryan,

Thanks for the question!

The idea is that the more computations we need to make, the more plausible it is to make an error. Hence, instead of computing 10*9*8*7*6*5*4 / 7*6*5*4*3*2*1, we can cross out 7*6*5*4 from the top and the bottom and essentially get the 720 / 6 you mentioned at the end.

Other than that, symmetry in combinations is more interesting and useful in the pure math side of probability, where we use such properties to write proofs.

Best,
365 Vik

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