I did something at home today, that is, I measured a one-dollar coin.

The tools are: a set of rulers, a one-dollar coin and a colored pen.

First, draw the diameter of a dollar coin with crayons. Its diameter is 2.5 cm. Calculate the circumference of a circle, 2.5 times 3. 14 equals 7.85 cm. If you know the radius of a circle, you have to multiply 3. 14 by 2 to calculate the circumference of the circle.

I also know that the line segment connecting the center of the circle and any point on the circle is called diameter, which is generally represented by the letter R. The line segment passing through the center of the circle with both ends at the center is called radius, which is generally represented by the letter D. The center of the circle determines the position of the circle, and the radius determines the size of the circle.

I had nothing to do at home today, so I found an old four-wheel drive wheel. I began to measure its circumference. It's hard to find points, so I borrowed several methods from a class. Because the wheel is installed here, it is difficult to measure. Finally, I drew a circle on the paper according to the size of the wheel.

Measure the diameter. 3,14× 2,5 = 7,85 (cm).

This is really an interesting measurement!