5C2 is asking how many combinations of 2 can be made out of 5 items.
The formula to solve this is:
C(n,r) = n! / (r!(n-r)!)
N is the number of items and r is the sample
Replace n and r and solve:
5! / (2!(5-2)!)
a number with an exclamation point, means to multiply that number by all the numbers below it.
5! = 5 *4 *3 *2 *1 = 120
2! = 2*1 =2
5-2 = 3
3! = 3*2*1 = 6
Now you have 120 / 2*6 = 120/12 = 10
The answer is 10.
