Westonci.ca is your go-to source for answers, with a community ready to provide accurate and timely information. Experience the convenience of finding accurate answers to your questions from knowledgeable experts on our platform. Join our platform to connect with experts ready to provide precise answers to your questions in different areas.

A person going to a party was asked to bring 3 different bags of chips. Going to the store, she finds 13 varieties.How many different selections can she make?

Sagot :

In this problem we are given that a person who wants to go to a party would like to bring 3 different bags of chips; and also, that he/she has 13 varieties.

As she has differents options to choose, we see that this one is a problem of permutations or combinations. But the order of the chips the person brings does not matter, and so, we have to find a combination. We remember then that the equation for finding a combination of n objects and k possibilites is given by the following binomial coefficient

[tex]\binom{n}{k}=\frac{n!}{k!(n-k)!}[/tex]

Where the symbol ! represents factorial (the product of the number to the number). For example,

[tex]4!=4\cdot3\cdot2\cdot1=24[/tex]

Now, in our exercise, we have that the person has 13 varieties and has to choose 3 of them. We have to calculate then:

[tex]\binom{13}{3}[/tex]

For doing so, we will start by replacing the values on the formula:

[tex]\begin{gathered} \binom{13}{3}=\frac{13!}{3!(13-3)!} \\ =\frac{13!}{3!(10)!} \\ =\frac{13\cdot12\cdot11\cdot10\cdot9\cdot8\cdot7\cdot6\cdot5\cdot4\cdot3\cdot2\cdot1}{3\cdot2\cdot10\cdot9\cdot8\cdot7\cdot6\cdot5\cdot4\cdot3\cdot2\cdot1} \end{gathered}[/tex]

And cancelling the equal terms, we obtain:

[tex]\begin{gathered} =\frac{13\cdot12\cdot11\cdot\cancel{10}\cdot\cancel{9}\cdot\cancel{8}\cdot\cancel{7}\cdot\cancel{6}\cdot\cancel{5}\cdot\cancel{4}\cdot\cancel{3}\cdot\cancel{2}\cdot\cancel{1}}{3\cdot2\cdot\cancel{10}\cdot\cancel{9}\cdot\cancel{8}\cdot\cancel{7}\cdot\cancel{6}\cdot\cancel{5}\cdot\cancel{4}\cdot\cancel{3}\cdot\cancel{2}\cdot\cancel{1}} \\ =\frac{13\cdot12\cdot11}{3\cdot2} \\ =\frac{13\cdot12\cdot11}{6} \\ =13\cdot2\cdot11=286 \end{gathered}[/tex]

This means that the person would be able to do 286 different selections.