To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(4a)(5ab) + (5a²)(3b)
(4 x 5)(a x a x b) + (5 x 3)(a² x b)
(20)(a¹⁺¹ x b) + (15)(a²b)
20a²b + 15a²b
35a²b

A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

The volume of a cylinder is πr²h:

v = πr²h
v = π(3² x 6)
v = 54π

A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(6²) + 2π(6 x 3)
sa = 2π(36) + 2π(18)
sa = (2 x 36)π + (2 x 18)π
sa = 72π + 36π
sa = 108π