Mark Porto and June Porto

Hackensack School District

TOPIC:

This project helps students understand the relationship between two scales (the Celcius and Fahrenheit scales) using the point-slope formula and determine the slope of the line from two points. Students will also understand the formula for conversion between both scales using the point-slope formula and determine the slope of the line from two points.

LEVEL:

Grades six through ten

TI-82 PROFICIENCY:

A basic understanding of TI-82 commands is required.

CLASS TIME:

Three class periods

Steps

Step 1: Determine the slope from two points

0 Celcius = 32 Fahrenheit

100 Celcius = 212 Fahrenheit

slope (m) = y2-y1/x2-x1

100-0/212-32 = 100/180 = 5/9 = the slope

Step 2: Determine the formula using the slope and one point

y-y1= m(x-x1)

y-0 = 5/9(x-32) = 5/9x - 17.778 = The formula to convert Fahrenheit to Celcius

Step 3: Find the slope using two points on TI-82

Type: (100)/(212-32) Enter

(The answer will be in decimal form: .5555556.)

Type Math 1 Enter

(This will change the answer to a fraction. The answer will be 5/9 -- the slope.)

Step 4: Find the equation of the line using the point-slope forumula and TI-82

Type Y= (5/9)(x-32)

(Note: the value for y1 in the equation is 0.)

Type Window Enter -100 Enter 200 Enter 1 Enter -100 Enter 200 Enter 1

Type Graph Zoom 3 Enter

Use Trace to move along the line and see the Fahrenheit values (x values) and corresponding Celcius valuews (y values).

Type 2nd Graph

Use arrow keys to see the values of x (Fahrenheit) and values of y (Celcius).

NOTES TO TEACHER:

Using TI-82, students can visualize the relationship between the two temperature scales and see the corresponding values (between Celcius and Fahrenheit) on a graph. This way, students will be able to understand the formula which converts values from one scale to the other.