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!

r!(nr)!
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!(41)!=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.