Question

There are 15 students And a social studies class. Two students will be selected to present their term projects today. And how many different orders given to students to be selected?

A. 849
B. 105
C. 420
D. 210

Answer 1

I think the answer is B but I am not quite sure

Answer 2

The correct option is B.

Explanation:

Total number of students = 15

Number of selected students = 2

Total number of ways to select r items from n items is

`^nC_r=(n!)/(r!(n-r)!)`

Total number of ways to select 2 items from 15 items is

`^(15)C_(2)=(15!)/(2!(15-2)!)=105`

`^(15)C_(2)=(15* 14* 13!)/(2* 1* 13!)=105`

Therefore the correct option is B.