Posted by **Emma B** on Sunday, September 12, 2010 at 6:47pm.

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

n!

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r!(n-r)!

a:find 4C1

b:Find 5C0 and 5C5

c: Find 7C1, 7C2, 7C3

- Pre Calc -
**bobpursley**, Sunday, September 12, 2010 at 7:05pm
What is your question on this? The formula gives the algorithm.

- Pre Calc -
**Jen**, Sunday, September 12, 2010 at 7:42pm
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.

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