Multiply two numbers using a Parabola! By making the correct parabola corresponding to square roots of numbers, you can find simple multiplication product of two numbers on the Y axis.

## Step 1: Gather Materials

- White Paint

- Nails (around 2"): 26

- Sharpie

- Yardstick (really long ruler) x2

- Wooden board: cut down to 26"x34"

- String, about 5'10" or 70"

## Step 2: Paint

Paint the board white.

## Step 3: Measurements!

Make a pencil mark at each one-inch mark of your board on all sides. There should be 26 marks on the top and bottom. There should be 34 marks on the two sides

At the 13" mark on the top, draw a line directly down to the 13" mark on the bottom, this will be the Y axis of your parabola!

## Step 4: Label Top and Bottom Marks

Label your top and bottom 1" marks starting on the left side 12-1(the actual left side of your board represents 13) once you get to the center label it 0 and going to the right label them 1-12 (the actual right side of your board represents 13). Do this on the bottom of your board also.

## Step 5: Label Middle Line

At each 1" interval, label the line 5, 10, 15, 20 and so on, until you get 170 at the bottom.

## Step 6: 5'ing the Center Line

Between each mark on the center line make 4 equal marks, dividing your line into 170 equal parts.

## Step 7: Plotting Your Points

Lay your Yardstick on the mark labelled 4 on the right side of your board, make sure it is at an exact right angle and crosses the 4 labelled on the bottom of your board. Take your other Yardstick and (making sure it is at a right angle) cross it through the 16th mark on your central line. Do the same for the rest of your points on both sides:

13 crosses at 169

12 crosses at 144

11 crosses at 121

10 crosses at 100

9 crosses at 81

8 crosses at 64

7 crosses at 49

6 crosses at 36

5 crosses at 25

4 crosses at 16

3 crosses at 9

2 crosses at 4

1 crosses at 1

Connect each of your points!

## Step 8: Nailing and Stringing

At each of the points you found, nail in a nail, just far enough so it still sticks out at least a centimeter. In the top right corner of your board nail a nail about 1x1 inch in. Tie your 70" string around the nail. To use the calculator, choose two numbers 13 and under, string the string from one number on the side to the number on the other side, over one number and under the other. The point the string crosses the center line is the product of those two numbers.

## 3 Discussions

2 years ago

Please use this as your SAT calculator! :)

2 years ago

I love this. I have to show a few math teachers.

2 years ago

That's a neat tool :)