Question

A medical researcher needs 7 people to test the effectiveness of an experimental drug. If 15 people have volunteered for the test, in how many ways can 7people be selected?

Answer 1

Given:

A medical researcher needs 7 people to test.

15 people have volunteered for the test.

To find:

We need to find a number of ways to select 7 from 15 people.

Step-by-step explanation:

The number of ways to select 7 from 15 people can be found by the given formula.

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

Substitute n=1`5 and r=7 in the formula.

`15C_7=(15!)/(7!(15-7)!)`

`15C_7=(15*14*13*12*11*10*9*8!)/(7*6*5*4*3*2*(8)!)`

`15C_7=15*13*11*3`

`15C_7=6435`

Final answer:

The number of ways = 6435 ways.