# Why You Should Never Talk to π

In an earlier blog entry, we discussed the role of trigger activities in the learning of new topics in maths. If you missed that discussion, click __here__ to catch up.

*The following activities are extracted from the Mad Maths section of the topic of Circles (Primary 6 Mathematics Joyous Learning curriculum)*

To introduce the topic of Circles to students, show them an __animated video clip__ on the history of the number π.

How well do you know the special mathematical constant π?

Test yourself by having a go at filling in the blanks below.

**7 interesting facts about π**

The symbol is the sixteenth letter of the _____ alphabet.

The value of π can be obtained by taking the _____ of a circle divided by its diameter.

When π is represented as a decimal, it has an _____ number of digits.

22/7 is an _____ of the value of π; there is no common fraction that represents π's exact value.

There is a special day in the year dedicated to π. It's _____, known as (what else?) Pi Day!

Piphilology is the process of creating and using techniques to _____ spans of digits of π.

The current Guinness World Record for memorising the most decimal places of π is _____. The record was set in 2015 by Suresh Kumar and it took him over 17 hours to recall all the digits!

Answers to the quiz can be found at the end of this article. Hope you had fun learning some facts about π!

It is often fun and more satisfying to discover something for ourselves rather than to be informed directly. Click __here__ for the earlier discussion on the rewards of the discovery process in the learning of maths. In maths, carefully-designed activities pitched at students’ ability enable them to make independent discoveries in their learning.

Try out the following hands-on activities with your child to let him or her discover a mathematical constant. No prizes for guessing what constant in question.

**Activity 1**

You'll need the following items:

3 x circular objects (e.g. ping pong ball, tennis ball, soft drink can (cross-section), etc.)

1 x ball of string

1 x measuring tape

Use the ball of string or the measuring tape to measure the circumference of the first circular object and record the value as C. Use your ruler to measure the diameter of the circular object and record the value as D. Use your calculator to compute the operation C ÷ D. What is the answer?

Now, repeat the same steps for the second and third circular objects. Your child will discover that the answer to C ÷ D stays the same, no matter which circular object they use.

This activity makes learning more meaningful because students do not merely remember π as an arbitrary value. Instead, they learn for themselves how the value of π is derived.

**Activity 2**

Earlier, you must have wondered how someone was able to memorise 70,000 digits of π! Sure, it's difficult, but anyone (seriously) can do it if they put in enough effort.

This activity demystifies the feat of memorising such a great number of digits. At the same time, students also learn a nifty technique to remember random numbers.

Take a look at the table below.

Note that the digits that make up pi are the number of letters in the corresponding word.

Now, Use the template below to come up with your own sentence to remember the first 15 digits of π! Once 15 digits is no longer a problem, extend it 100 digits, 1000 digits, or till your brain hurts.

Oh, and why should you never to talk to π? Because he'll go on forever...

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