2. The Formula Sheet You Get

On test day the GED® gives you a formula sheet. You do not need to memorize these -- but you do need to know which formula to grab. The most-used ones:

Area

• Rectangle: \(A = lw\)
• Triangle: \(A = \tfrac{1}{2}bh\)
• Circle: \(A = \pi r^2\)
• Trapezoid: \(A = \tfrac{1}{2}(b_1 + b_2)h\)

Perimeter / Circumference

• Rectangle: \(P = 2l + 2w\)
• Circle: \(C = 2\pi r = \pi d\)

Volume

• Box (rectangular prism): \(V = lwh\)
• Cylinder: \(V = \pi r^2 h\)
• Cone: \(V = \tfrac{1}{3}\pi r^2 h\)
• Sphere: \(V = \tfrac{4}{3}\pi r^3\)

Algebra & Geometry

• Pythagorean theorem: \(a^2 + b^2 = c^2\)
• Slope: \(m = \dfrac{y_2 - y_1}{x_2 - x_1}\)
• Slope-intercept line: \(y = mx + b\)
• Quadratic formula: \(x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}\)

Percent & rate ideas to keep in your head

• Percent change \(= \dfrac{\text{new} - \text{old}}{\text{old}}\)
• Distance \(= \text{rate} \times \text{time}\)