You own 7 pairs of jeans and want to take 2 of them with you on vacation. In how many ways can you choose 2 pairs of jeans?
A. 60
B. 21
C. 20
D. 10
The answer is D. 10
The formula to use here is the combinations formula, which is:
nCk = n! / (k! * (n-k)!)
where n is the number of items to choose from and k is the number of items to choose.
In this case, n = 7 and k = 2, so we have:
7C2 = 7! / (2! * (7-2)!)
= 7! / (2! * 5!)
= (7 * 6 * 5!) / (2 * 1 * 5!)
= 21
Therefore, there are 21 ways to choose 2 pairs of jeans from 7 pairs.