Question

Evaluate the expression: 20C4

Answer 1

4845

Explanation:

Given 20C4 this means ₂₀C₄

Apply the formula for combinations without repetition

`nCr=(n!)/((n-r)!.r!)`

where

n is the number of things to choose from and r is what you choose from them

Given that ;

n=20

r=4

n-r=20-4=16

Insert values in the equation

`20C4=(20!)/(16!*4!) \\\\\\=(16!*17*18*19*20)/(16!*4!) \\\\\\=(17*18*19*20)/(1*2*3*4) \\\\\\=17*19*15\\\\\\=4845`