## Lesson Objectives

Discuss and start to critically analyze the stigmatization of using body parts in math. Potential introduction to proofs or review of proofs and looking at bases in different ways (i.e. introduction to modules)

By the end of this lesson students will have an algebraic and cultural understanding of the finger multiplication method.

## Lesson Outline

#### Direct Teaching: How the finger multiplication method works (10 mins)

- Introduce the finger multiplication method with its history and teach the algorithm. After showing the algorithm, go through some examples with the students, following along with the algorithm for each example.

#### First discussion: **Small group or class discussion** (10 mins)

- Either in small groups, or as a class, discuss how using this method might be useful to younger students.
- To tie this into the next lesson:
- Finish with a quick class lead discussion, and, if not already brought up by students, prompt the idea that for some young students, this may be the method their parents taught them.

**Making an algorithm: **(30 mins)

**Making an algorithm:**- Ask the students to describe the algorithm as an equation in terms of x and y. Once they have an equation, they should show it works.
- (Prove their equation equals x*y).
- Prompts to help students start:
- If you start with an example, how does it work? You can choose to start with 6 times 7, and show how 6 times 7 (
*x*times*y*) is obtained from the multiplication method.- Write out the entire equation:

6*7=(1+2)*10+3*4

- Write out the entire equation:
- What is the domain and range/restriction of x and y? (This is to prompt the recognition of using 5’s in the equation)

- If you start with an example, how does it work? You can choose to start with 6 times 7, and show how 6 times 7 (
- Extra time (or for higher grades):
- If there is extra time, ask the students to recreate the algorithm and equation for someone with 4 fingers on each hand.
- They can also make it with a partner, creating an algorithm and formula for someone with 20 fingers.

##### Conclusion (15 mins)

- Finish the lesson going over the common equation for the algorithm:
- xy=10(x+y-10)+(x-5)(y-5)

Conclude in reviewing the equation, and also tying it back to the discussion from the beginning of the class.

## Downloadable Materials & Links

## Categories

- Intermediate Lesson Plan (2)
- Lesson Plan (5)
- Secondary Lesson Plan (3)
- Selected Presentations and Papers (8)