Stage 4 – π = 3.141
Pi= 3.14159… is the number you need to multiply a circle’s diameter to get the circumference. The interesting point about pi (Greek letter for ‘p’ probably chosen to stand for ‘periphery’ is that this sequence of numbers will continue on forever, never ending, and never getting caught up in a repetitive loop as with recurring decimals when converting fractions to decimals. It would be worthwhile exploring the history of this elusive number throughout the ages and for students to understand that this number has only been in use over the last 250 years.
Strategy
Students can:
- calculate the circumference of a circle using pi
Activities to support the strategy
The Golden Rule
= 3.14159… is the number you need to multiply a circle’s diameter to get the circumference. The interesting point about pi (Greek letter for ‘p’ probably chosen to stand for ‘periphery’ is that this sequence of numbers will continue on forever, never ending, and never getting caught up in a repetitive loop as with recurring decimals when converting fractions to decimals. It would be worthwhile exploring the history of this elusive number throughout the ages and for students to understand that this number has only been in use over the last 250 years.
Activity 1
The teacher discusses how to calculate the circumference of a circle, given either the radius or diameter.
Introduce the significance and value of pi.
- Use pi to calculate the circumference of different circles using the radius and the diameter.
- Students could write their own problems to calculate the circumference and have a partner solve.
Students use the following interactive tasks to explore circles.
- Exploring circle geometry properties interactive tasks investigates the parts of the circle including angles, chords, and tangents. Included are print activities, solutions, learning strategies, and a circle pong game.
- Exploring the diameter and circumference of circles video highlights how circles can be found all around us. The interactive tasks allow students to explore the relationship between circumference and diameter. A print activity is included.
- Illuminations - Circle tool
References
Australian curriculum
ACMNA186: Investigates the concept of irrational numbers including pi
NSW syllabus
MA4-12MG: Calculates the perimeter of plane shapes and the circumference of circles
Teacher resources
Lesson plans and activities
Students can learn about calculating the circumference and diameter of a circle.
- mathgoodies.com/lessons/vol2/circumference
- pbs.org/wgbh/nova/archimedes/pi
- learner.org/courses/learningmath/measurement/session7/part_a/index.html
