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- Formulas for Common Geometric Shapes

# Formulas for Common Geometric Shapes

By Mary Jane Sterling

Part of Algebra Workbook For Dummies Cheat Sheet

Depending on the algebra problem, you’ll need to know some geometry. The following represents some of the most common shapes in geometry and their formulas for perimeter, area, volume, surface areas, and circumference:

Two-Dimensional Shapes
Shape |
Perimeter/Circumference |
Area |

Rectangle |
P = 2(l + w) |
A = lw |

Square |
P = 4s |
A = s^{2} |

Triangle |
P = a + b + c |
A = 1/2bh |

Trapezoid |
P = a + b_{1} + c + b_{2} |
A = 1/2h(b_{1} + b_{2}) |

Isosceles Trapezoid |
P = 2w + b_{1} + b_{2} |
A = 1/2h(b_{1} + b_{2}) |

Circle |
C = πd = 2 π r |
A = π r^{2} |

Three-Dimensional Shapes
Shape |
Surface Area |
Volume |

Box |
SA = 2lw + 2lh + 2wh |
V = lwh |

Sphere |
SA = 4 π r^{2} |
V = 4/3 π r^{3} |

Cylinder |
SA = 2 π r(r + h) |
V = π r^{2}h |