Learn the relationship between the radius, diameter, and circumference of a circle.

*To find the diameter, measure the circle from its left-right points [divide the circle in half and measure the line you made, make sure the line is straight]. Suppose you get 10in, that is your …

Now you could imagine, it's oftentimes very useful to think about the relationship between the diameter and a circumference, but it's not very useful to write 3.14159, and you can keep on …

A circle has a circumference of 113.04 units. What is the diameter of the circle? Use 3.14 for π and enter your answer as a decimal.

If we say the circumference is 1600 pi, and this is equal to pi times the diameter, we can just divide both sides by pi to get the diameter, which is going to be 1600.

Describe π as the ratio of the circumference of a circle to its diameter. Describe the diameter and circumference in terms of π and each other.

Another way that we could approach it is we know we have some angles inscribed angles on this circle, and we know that if an inscribed angle intercepts a diameter, then it's going to be a right …

We measured the size of the sun (about 1.3 million kilometers) using some basic observations and a little geometry! This illustration shows the approximate size of Earth compared to the …

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This led him to claim that the earth was about 8/3 the diameter of the moon. This is pretty close to the actual difference: the earth is about 3.7 times bigger than the moon.