Question

Barbara has 7 swimsuits. She needs to take 4 swimsuits on a vacation. In how many different ways can she choose 4 swimsuits out of 7

A. 35
B. 840
C. 24
D. 210

Answer 1

Answer: 35

Explanation:

Answer 2

You should use here the formula for combinations

`C_n^k=(n!)/(k!(n-k)!).`

In your case n=7, k=4, then

`C_7^4=(7!)/(4!(7-4)!)=(7!)/(4!\cdot 3!)=(4!\cdot 5\cdot 6\cdot 7)/(4!\cdot 2\cdot 3)=5\cdot 7=35.`

Answer: 35 ways, option A.