The number of ways six people can be placed in a line for a photo can be determined using the expression [tex]6![/tex]. What is the value of [tex]6![/tex]? [tex]\(\square\)[/tex]

Two of the six people are given responsibilities during the photo shoot. One person holds a sign and the other points to the sign. The expression [tex]\frac{6!}{(6-2)!}[/tex] represents the number of ways the two people can be chosen from the group of six. In how many ways can this happen? [tex]\(\square\)[/tex]



Answer :

To determine the number of ways to choose and organize two people out of six, where two specific people are given responsibilities, we can use the concept of permutations.

Permutations are used when the order matters, which is the case here since one person is holding the sign and another is pointing to the sign.

The formula for permutations when choosing and ordering [tex]\( k \)[/tex] out of [tex]\( n \)[/tex] is given by:

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

In this problem:
- [tex]\( n \)[/tex] is 6 (the total number of people),
- [tex]\( k \)[/tex] is 2 (the number of people chosen to hold responsibilities).

Let's apply these values to the permutation formula:

[tex]\[ P(6, 2) = \frac{6!}{(6 - 2)!} = \frac{6!}{4!} \][/tex]

Now, we can simplify by calculating the factorial expressions:

[tex]\[ 6! = 6 \times 5 \times 4 \times 3 \times 2 \times 1 \][/tex]
[tex]\[ 4! = 4 \times 3 \times 2 \times 1 \][/tex]

When we divide these two, the [tex]\(4!\)[/tex] terms cancel out:

[tex]\[ \frac{6!}{4!} = \frac{6 \times 5 \times 4 \times 3 \times 2 \times 1}{4 \times 3 \times 2 \times 1} = 6 \times 5 = 30 \][/tex]

So, the number of ways to organize two people out of six with specific responsibilities is:

[tex]\[ 30 \][/tex]

Therefore, the number of ways this can happen is [tex]\( \boxed{30} \)[/tex].