# Pre Calc

The symbol nCr, rea "n choose r" or "the number of combinations of n things taken r at a time" is the number:

n!
-----
r!(n-r)!

a:find 4C1
b:Find 5C0 and 5C5
c: Find 7C1, 7C2, 7C3

1. What is your question on this? The formula gives the algorithm.

posted by bobpursley
2. a)4!/1!(4-1)!=4 x 3 x 2/3 x 2, cancel out the 3's and 2's=4
You do b and c. Post your answers if you'd like them checked.

posted by Jen

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