Question

What is 9C7 ?
A. 66
B. 55
C. 45
D. 36

Answer 1

Answer:

D.36

Step-by-step explanation:

Remember, the formula to calculate combinations is nCr = n! / r! * (n - r)!, where n represents the number of items, and r represents the number of items being chosen at a time.

Answer 2

Answer:

D. 36

Step-by-step explanation:

The formula for a combination :

• ⁿCₓ = n! / (n - x)! x!

Here we have ⁹C₇.

• ⁹C₇ = 9! / (9 - 7)! 7! = 9! / 2! x 7!
• 9 x 8 x 7! / 2! x 7!
• 9 x 8 / 2
• 36