Question

The value of ${}^{2021}{\text{C}}_{2020}$ is

• A. $1$
• B. $2021$
• C. $2020$
• D. $2021\times 2020$

Answer 1

The correct option is B $2021$

Note:
${}^n{\text{C}}_r={}^n{\text{C}}_{(n-r)}$

So,
${}^{2021}{\text{C}}_{2020}={}^{2021}{\text{C}}_{(2021-2020)}$

$={}^{2021}{\text{C}}_1$

$=\frac{2021}{1}$

$=2021$