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Learning how to measure the space inside a flat shape using square units.
Imagine you want to cover your bedroom floor with soft foam tiles. How do you know exactly how many tiles to buy so you don't run out or have too many left over?
Area is the amount of space inside the lines of a flat shape. Think of it like the 'carpet' that covers a floor or the 'paint' that covers a piece of paper. To measure this space, we use square units. A square unit is a square where every side is exactly the same length, like inch or centimeter. When we find the area, we are simply asking: 'How many of these little squares can fit inside this shape?'
Quick Check
If you are 'painting' the inside of a square, are you finding the perimeter (the outside edge) or the area?
Answer
You are finding the area because you are filling the space inside the boundary.
The easiest way to find the area of a shape is to count the unit squares inside it. If a shape is drawn on a grid, you can just count them one by one! For example, if a shape is filled with small squares, we say its area is square units. It doesn't matter if the squares are arranged in a long line or a block; if there are of them, the area is still .
Look at a rectangle drawn on grid paper. 1. Count the squares in the top row: . 2. Count the squares in the bottom row: . 3. Since there are squares total, the area is square units.
Counting every square takes a long time if the shape is big. Luckily, rectangles are organized into rows and columns, just like an array in multiplication! To find the area of any rectangle, you can multiply the length (how long it is) by the width (how wide it is). The formula looks like this:
Imagine a garden that is feet long and feet wide. 1. Identify the length: feet. 2. Identify the width: feet. 3. Multiply them together: . 4. The area is square feet.
Quick Check
A rectangle has a length of units and a width of units. What is its area?
Answer
The area is square units ().
You have a giant poster that is inches long. You know the total area is square inches. How wide is the poster? 1. We know . 2. So, . 3. Think: times what equals ? 4. The width must be inches!
What is the definition of area?
A rectangle is units long and units wide. What is its area?
To find the area of a rectangle on a grid, you can either count the squares or multiply the side lengths.
Review Tomorrow
Tomorrow, try to explain to a friend why we use 'square units' to measure area instead of just using a regular ruler line.
Practice Activity
Find a rectangular object in your house (like a book or a rug). Measure its length and width in inches, then multiply them to find the area!