$\text{Pi} = \frac{\text{Circumference}}{\text{Diameter}}$

or simply:

$\pi = \frac{C}{d}$

This means: if you divide the circumference of any circle by its diameter, you always get the same number — pi!

You can discover pi yourself by measuring real circular objects:

Steps:

1. Take a circular object (like a cup, plate, bucket lid, or bottle top)
2. Wrap a string around the edge of the object
3. Mark where the string completes one full round
4. Measure the length of the string — this is the circumference
5. Measure the diameter (across the circle through the centre)
6. Divide the circumference by the diameter

Example:

Suppose a plate has:

• Circumference = 62.8 cm
• Diameter = 20 cm

$\text{Pi} = \frac{62.8}{20} = 3.14$

If you try with a cup, bucket, or lid, you will get approximately the same result!

• Decimal form: π ≈ 3.14 (rounded to 2 decimal places)
• Fraction form: π ≈ 22/7
• Exact value: π = 3.141593... (the decimal goes on forever!)

• Pi is the same for every circle — big or small
• Pi connects the size of a circle to its circumference
• The value of pi is approximately 3.14 or 22/7
• We use pi when calculating circumference and area of circles

A pupil measured a wheel and found its diameter is 14 cm. Using π = 22/7, what is the circumference of the wheel?

Solution:

$C = \pi d$

$C = \frac{22}{7} \times 14$

$C = \frac{22 \times 14}{7}$

$C = \frac{308}{7}$

$C = 44 \text{ cm}$

Therefore, the circumference of the wheel is 44 cm.

In Tanzania, understanding pi is useful in everyday life. For example, when a tailor needs to add decorative border tape around a circular table mat, they use pi to calculate how much tape is needed. If the table mat has a diameter of 70 cm, the tailor calculates the circumference using pi to know the exact length of tape to buy, avoiding waste and saving money.