# Counting problem

Question 1:

My question is how do I know when to use the permutation theorem or comination theorem?

Theorem in paint document

I'm asking because I would have used permutation thm. on 46 but I was wrong.

Problem 46 b. and Problem 47 a. seem similar. The two main differences that I see are
1. 46. We are given a group of ten people to choose from
47. We are given a group of six people to choose from

2. 46. Placement of bride and groom does not matter (Bride and groom must be in picture- No reference to placement)
47. Placement of bride and groom matters (Bride must be next to groom)

Therefore do I use combination if Placement matters?
And permutation if placement does not matter?

Question 2:
How would the answer to 46 b change if bride must be next to groom?
and
how would answer to 47 a change if bride and groom must be in picture?

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## Answers and Replies

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haruspex
Homework Helper
Gold Member
I agree with you. The answer given to 46b is for choosing the 6 people, not for arranging them in a row.
If you care to post your answers to 46a,b,c I (or someone) will check them.

for number 47 part a. If i changed the problem to, the bride and groom must be in the picture then the answer would be,
4 choose 4 = 1.

haruspex