A radius and a diameter both have to ___________.

go through the center of the circle

i hate math but i should study it.

A radius and a diameter both have to relate to the same circle.

To understand how a radius and a diameter are related, let's first define what they are:
- A radius is a line segment that connects the center of a circle to any point on the circle. It is typically denoted by the letter 'r'.
- A diameter is a line segment that passes through the center of a circle, connecting two points on the circumference of the circle. It is typically denoted by the letter 'd'.

Now, the relationship between a radius and a diameter is that the diameter of a circle is always two times the length of its radius. In other words, the diameter is equal to twice the radius (d = 2r).

So, to answer your question, a radius and a diameter both have to relate to the same circle, and the diameter is always double the length of the radius.