To celebrate Pi Day (3/14), have fun with MyPiDay, developed last year by Stephen Wolfram and company. Enter your birthday or any other number and see where it first appears in pi.
In honor of Pi Day (3/14/16 = 3.1416), here's a page from The Giant Golden Book of Mathematics (1958) that shows you how to calculate Pi by dropping toothpicks on a wood floor.
Read the rest
We see circles everywhere. The wheels of automobiles, the rims of cups, and the faces of nickels and quarters are all circles. The sun and the full moon look like circles in the sky.
The distance across a circle, through its center, is called the diameter of the circle. The distance around the circle is called its circumference. Measure the diameter of a quarter, and you will find that it is about one inch long. You can measure the circumference of the quarter, too. First wind enough string around it to go around once. Then unwind the string, and measure it with a ruler. You will find that it is about three times as long as the diameter. Measure the circumference and diameter of the rim of a cup and you will get the same result. The circumference of any circle is a fixed number times the diameter. This fixed number cannot be written exactly as a fraction or decimal, so we use the Greek letter pi to stand for it. It is almost equal to 3-1/7, or 3.14.
Strange as it may seem, there is a way of calculating the value of pi by dropping a stick on the floor. The floor has to be made of planks of the same width. Use a thin stick, such as a toothpick, that is as long as the planks are wide.