Classroom kit

Sheet 1 of 4Name: ____________________ Class: __________

Find your birthday in π

Every birthday is hiding somewhere in the digits of π. Look yours up on Hidden in π (or use a friend's, or a favourite number: nothing private needed) and fill in the table.

1. Which way of writing your birthday was found first? Which was found last?
2. Round your deepest answer to the nearest thousand, million or billion: about how deep is it?
3. Why does a birthday written with eight digits hide so much deeper than one written with four?

Hidden in π classroom kit

Sheet 2 of 4Name: ____________________ Class: __________

The π digit hunt

These are the first 1,000 decimals of π: the digits after the 3. Each row starts with the decimal place of its first digit. Find each target and write down where it first appears.

1. The very first 0. Decimal place: ______
2. 42, the answer to everything. Decimal place: ______
3. Three 1s in a row. Decimal place: ______
4. 360, the degrees in a circle. Decimal place: ______
5. 100, a nice round number. Decimal place: ______
6. Six 9s in a row (the Feynman point). Decimal place: ______

My own two-digit number: ______ It first appears at decimal place: ______

Hidden in π classroom kit

Sheet 3 of 4Name: ____________________ Class: __________

Measure π with string and paper plates

You need string, a ruler and round things: paper plates, tins, rolls of tape. Wrap the string around the edge to measure the circumference, then measure straight across the middle for the diameter. Divide the first by the second.

1. Which answer was closest to 3.14? Was it a big object or a small one?
2. Work out 22 ÷ 7 to four decimals. How many decimals match π?
3. Work out 355 ÷ 113 to seven decimals. How many decimals match π?

Hidden in π classroom kit

Sheet 4 of 4Name: ____________________ Class: __________

Answer key

Find your birthday in π

Answers depend on the birthday. The four-digit form usually turns up within the first ten thousand decimals, the six-digit form within about a million, the eight-digit form within about a hundred million. Each extra digit makes a number about ten times harder to find, so two extra digits push it about a hundred times deeper.

The π digit hunt

Decimal places count from the first digit after the 3. (decimal 1).

• The very first 0: decimal place 32
• 42, the answer to everything: decimal place 92
• Three 1s in a row: decimal place 153
• 360, the degrees in a circle: decimal place 285
• 100, a nice round number: decimal place 854
• Six 9s in a row (the Feynman point): decimal place 762

Measure π with string and paper plates

Answers crowd around 3.1: string stretches and rulers wobble. Big objects usually give the best answers, because a small measuring mistake matters less on a big circle. 22 ÷ 7 = 3.1429 (two decimals match). 355 ÷ 113 = 3.1415929 (six decimals match).

Hidden in π classroom kit