Question

On a 12 problem test how many ways can 2 problems correct and 10 questions wrong?

Answer 1

Basically we have to calculate how many ways 2 objects can be chosen from 12?

We use this formula

where n = 12 and r =2

12! / (2!) * (12 -2)! =

12! / (2) * 10! =

12 * 11 / 2 = 132 / 2

= 66 ways

Explanation: