lonesome307 wrote:

Thanks guys for the quick response. How would I know when I need to use these permutation?? formula?

saurster wrote:

10C4 = 10!/((10! - 4!)*4!)

= 10*9*8*7/4*3*2*1

= 210 (E)

This is actually a combination problem because order does not matter. One of the ways I differentiate between the two is if the question is asking for an arrangement, order will matter so I use permutation. If the question is asking about selection or number of ways of listing something, we apply combinatorial principle. The reason why is because with combination problems order does not matter so we will be double counting. Hope that helps and good luck!