## Lesson Plan # 22 - Permutations

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- (5 min) Mental Math
- Start with 26, double it, then add 9 [61]
- What is 30% of 70? [21]
- What is 35% of 220? [70]
- What is 22% of 110? [22]
- If 100% of 60 is 60, what is 150% of 60? [90]

- (10 min) Introduce permutations:

- Follow the discussion in the handout. Write the permutations of the
words "WHO" and "STOP" on the board.
- Have students find all the permutations of one of these words: "GIRL",
"COAT", or "WALK". Have one student come up and write all the permutations
on the board with the help of the other students. Guide them so that they
approach it in an orderly way: first all the permutations starting with
the first letter, then all the permutations starting with the second
letter, etc.
- You might want to do one of the following:
- Bring a bag of "skittles" and explore how many different colors there
are, and how many different ways they can be ordered.
- Put 4 names on slips of paper, and then explore how many different
orderings the students can find.

- (15 min) In-class exercise, part 1.
- (5 min) Discuss permutation subsets
- Follow the discussion on page 2 of the handout
- You may want to do one of the following:
- Explore how many 2-candy skittles groups can be formed
- Explore how many 2-person groups can be formed from the names on the
slips of paper used earlier

- Try this example:

A club of 4 kids chooses a president and vice-president. Choose 4 names
from your class and explore the number of president-vp pairs there are.
(answer: 4 x 3 = 12)

- (Remainder of class) In-class
Exercise, part 2

- Hand out homework as students successfully complete the in-class
exercise.