# 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.

## 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.