Question

Sir? sir? are u there? help me -_-

Answer 1

Answer:

a) The easiest way is to use a calculator such as a Casio brand or Sharp brand and key in 9C7 to get 36.

However, you can also use this formula: $nCr=\frac{n!}{r!(n-r)!}$ where n is the total number of items and r is how many you are selecting.

Plug in values:

$\frac{9!}{7!(9-7)!} =\frac{9!}{7!*2!}=\frac{9*8}{2!}=36$

b) The easiest way is to use a calculator such as a Casio brand or Sharp brand and key in 9P7 to get 181440.

However, you can also use this formula: $nPr=\frac{n!}{(n-r)!}$ where n is the total number of items and r is how many you are selecting.

Plug in values:

$\frac{9!}{(9-7)!} =\frac{9!}{2!}=9*8*7*6*5*4*3=181440$