Radius-the line drawn from the center of a circle to the rim of the circle.
Ratio-an expression that means the reletive parts of a whole number.
Ray-a line that starts at a certain point and goes on forever.
Reciprocal-the inverse of a number.
Rectangle-a four-sided shape with two matching sides opposite each other, and two shorter ones opposite each other.
Remainder-the number left when a number does not divide evenly.
Right Angle-an angle of 90 degrees.
Rotate-to turn around a center point.
Round-to estimate.