# Lesson 15 — Activity 1: Estimating and Calculating the Area of Rectangles

#### Area is a measure of how much space there is inside a shape. It is the number of square units required to cover a 2-D object. #### Estimating the Area of Rectangles A rectangle is a four-sided shape that has two sets of two sides that are equal in length. The longer sides are called the length while the shorter sides are called the width. All four corners are right angles. Right angles are usually shown by having a square drawn in the corner where the right angle is. #### The area of a rectangle can be estimated using a variety of methods. One method is to use grid paper. Count the number of squares inside the shape. Each square is one unit. #### Estimate the area of the following shape. You can prove your answer by using the geoboard once again. #### For example, let's say you have a rectangle with a length of 4 mm and a width of 2 mm and you want to know what the area is, you could calculate it this way: #### What if you had a rectangle that was 90 cm long and 27 cm wide? What would its area be? Use the formula above and put the unit in your answer. (You may use a calculator to solve.)

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