If you're finding diameter or radius based on circumference, use the formula C = πd. You would divide the circumference by pi to get the diameter, then divide the diameter by 2 to get the radius.
If you're finding diameter or radius based on area, use the formula A = πr^2. You would divide the area by pi, then find the square root of that value which is the radius. Just multiply the radius by 2 to find diameter.
Draw two straight parallel lines and label with units and arrow as the end Draw a tick mark through both lines and label with given ratio. Start with 0 and 0 on each number line. Label the units of each number line.
