Lesson · Grade 7 · Mathematics
Where pi comes from
- Grade 7
- Mathematics
- 1 min 9 s
- British Columbia
- BC7-MA-47
A circle 10 cm across has its circumference unrolled into a straight line, where just over three diameters fit, and the line measures about 31.4 cm, so 31.4 ÷ 10 = 3.14. Circles 5 cm and 20 cm across give the same answer, which is the number we call pi, so pi is the circumference of any circle divided by its diameter, about 3.14.
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In one sentence
The question this lesson answers
Where does the number pi come from?
This circle has a diameter of 10 centimetres.
Transcript
What the lesson says
Where does the number pi come from?
This circle has a diameter of 10 centimetres.
The circumference is the distance all the way around it.
Imagine unrolling the circumference into a straight line.
How many diameters fit along this line?
Three fit, with a little bit left over.
The line is about 31.4 centimetres long.
Now divide the circumference by the diameter.
31.4 divided by 10 is 3.14.
Now try a smaller circle and a bigger one.
Every time, the answer is about 3.14.
This special number is called pi.
Its digits go on forever, so we often use 3.14.
Pi is the circumference of any circle divided by its diameter.
Curriculum
Where this fits
- British Columbia, Grade 7
Mathematics, Geometry and measurement: circumference and area of circlesBC7-MA-47
Previous: Radius, diameter and circumferenceNext: Circumference from Diameter or Radius
The outcomes and strands follow the British Columbia curriculum.
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