Finding Missing Lengths

Main idea

Use the area formula to find a missing side Divide to solve for the unknown

Area

Space inside a shape measured in square units

Formula

Equation or rule to find the area

Base b

Bottom of a parallelogram

Height h

Straight up distance between bases not the slanted side

Rectangle or square formula

A = L × W

Parallelogram formula

A = b × h

Steps

Write the formula plug in what you know solve for the unknown check your answer

Example rectangle

Area = 36 cm2 Width = 12 cm Length = ? → 36 = L × 12 → L = 3 cm

Example parallelogram

Area = 72 cm2 Height = 9 cm → 72 = b × 9 → b = 8 cm

Remember

Use the formula first If one side is missing divide area by the known side Area ÷ side = missing side

Quick tip

Area is the result Side × Side = Area If one side is missing unmultiply by dividing

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Finding Missing Lengths Parallelograms 9 29 25