Question 1022189
.
{{{C[1]^4}}} = {{{(10*9*8*7)/(1*2*3*4)}}} = 10*3*7 = 210,


the number of combinations of 10 things take 4 at a time.


See the lesson <A HREF=http://www.algebra.com/algebra/homework/Permutations/Introduction-to-Combinations-.lesson>Introduction to Combinations</A> in this site.