There are 12 different cookies on a plate. Aiden will choose 3 of these cookies to pack in his lunch. How many different groups of cookies can he choose from 12?
A) 220
B) 320
C) 420
D) 440
I know the correct answer is A) 220, but I am not sure why?

Respuesta :

The number of different groups of cookies he can choose from the 12 cookies is 220

How to determine the number of different groups of cookies he can choose from the 12 cookies?

The given parameters are:

Number of cookies, n = 12

Selected cookies, r = 3

The number of different groups of cookies he can choose from the 12 cookies is calculated as:

Numbers = 12C3

The combination formula is represented as:

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

Substitute the known values in the above equation

Numbers = 12!/(12 - 3)!3!

Evaluate the difference in the above equation

Numbers = 12!/9!3!

Expand the above equation

Numbers = 12*11*10*9!/9!3!

Evaluate the quotient

Numbers = 12*11*10/3!

Expand the above equation

Numbers = 12*11*10/3*2*1

Evaluate the products

Numbers = 1320/6

Evaluate the quotients

Numbers = 220

Hence, the number of different groups of cookies he can choose from the 12 cookies is 220

So, the complete parameters are:

Number of cookies, n = 12

Selected cookies, r = 3

Number of selection = 220

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