Glossary 341principal The principal is the amount of money borrowed or invested. The rate is the percent
of the principal that will be paid in interest each year.
prism A prism is a polyhedron with two parallel faces connected by parallelograms.
product The result of the multiplication is the product.
proper fraction A proper fraction is one whose value is less than one, and an improper fraction
is one whose value is more than one.
proportion A proportion is two equal ratios. The means of a proportion are the two middle
numbers. The extremes are the first and last numbers.
protractor A protractor is a circle whose circumference is divided into 360 units, called
degrees, which is used to measure angles.
pyramid A pyramid is a polyhedron composed of a polygon for a base surrounded by triangles
that meet at a point.
Pythagorean theorem A mathematical relation that states that in a right triangle, the square
of the hypotenuse is equal to the sum of the squares of the other two sides. It is often expressed
as a^2 + b^2 = c^2.
Pythagorean triple A Pythagorean triple is a set of three whole numbers a, b, and c that fit the
rule a^2 + b^2 = c^2.
quadrilateral A quadrilateral is a polygon with four sides.
quotient The result of a division is called a quotient.
radius The collection of all points that sit at a certain distance, called the radius, from a set
point, called the center, forms the shape called a circle.
rate A comparison of two quantities in different units, for example, miles per hour or dollars
per day.
ratio A ratio is a comparison of two numbers by division.
rational numbers The set of all numbers that can be written as the quotient of two integers.
ray A ray is a portion of a line from one endpoint, going on forever through another point.
real numbers The name given to the set of all rational numbers and all irrational numbers.
reciprocal Two numbers are reciprocals if their product is 1. Each number is the reciprocal of
the other.
rectangle A rectangle is a parallelogram with four right angles.