If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: Geometry (all content)>Unit 7

Lesson 2: Area of rectangles

# Transitioning from unit squares to area formula

Lindsay finds the area of a rectangle both by counting unit squares and multiplying side lengths.  Created by Lindsay Spears.

## Want to join the conversation?

• I'm super confused. I CAN'T FIGURE THIS OUT! Can you help me? I'm having trouble understanding any of this. Could you explain it more?
• So how we are doing this is like we are multiplying so take a sheet of paper and draw a square not a perfect one but as good as you can, Then measure it so you will have to measure the length and the width guys, then you have to pick the size of the square you want to measure with , i example a centimeter so my square has two dimonsons example 6 and 7 multiply them 6x7=42 so my square is 42 centimeters , got it ?
• help me understand this!
• count the one side and the top. say its 2 and 4. do 2x4 and you have the area
• how is this gonna help us in life?
• You need to know how much paint to buy to paint rooms or carpet or tiling for floors. How much dirt you might need to build a garden, there are a lot of applications in life.
• that's true the only thing is when calculating the area of a square you can simply multiply one of the sides by itself since you know the other sides are all the same. and does it matter if it's a rectangle or a square in ares wouldn't still be length times width?
• That's correct. Squares are rectangles, but rectangles are not squares. Therefore, when finding the area of a rectangle, you can simply multiply the length by the width.
• This is really easy. Is it even high school geometry?
• Finding the area of a rectangle is much lower than high school level.

High school includes finding perimeters & areas of triangles, trapezoids, parallelograms, & circles, finding surface areas & volumes of prisms, cylinders, pyramids, cones, & spheres, finding lengths of missing sides of right triangles (Pythagorean theorem), using side length ratios in similar triangles to find missing sides, using angle relationships for parallel lines, intersecting lines, perpendicular lines, & polygons to find missing angles, using properties of circles to find missing lengths and/or angles, writing proofs using definitions, properties, postulates, & theorems, and more!

This seems like a lot, but as you build your understanding of math through the lower grade levels, you will become more prepared for high school geometry.

Have a blessed, wonderful day!
• - [Voiceover] This square is 1 square unit, so what is the area of Rectangle A? The first thing we're told is that each of these little squares equal 1 square unit, and then, we're asked to find the area of Rectangle A. Here's Rectangle A, and area is the space that it covers. So how much space does Rectangle A cover? How many square units does Rectangle A cover? One way to answer that would be count how many square units it covers, except they've covered up our square units. So, one idea's we could draw them back. Say you cover'em up, we'll draw them back in. So goin' like this, connect all these, and then, we should be able to count our square units. So we have one, two, three, four, five six, seven, eight, nine, 10, 11, 12. 12 square units. Rectangle A covers 12 square units, so it has an area of 12 square units. But this isn't the only way that we could've solved this. We could've also said, we could've also looked at this and said, okay, this top row is four square units long. One, two, three, four, has a length of four units. So that means the top row will have one, two, three, four square units inside of it. And then we coulda looked over on the side, over here, and said, well, how many rows of four will they'll be? It'll be one, two, three rows of four. So we'll have this row of four, and then a second row of four, and a third. So three times, we will have four square units. There's four square units at the top, another in the middle, and another at the bottom. Three times, we will have four square units. Or, we could go even farther than that. So we coulda done three times four, or we could look at this and say, okay, here's one column. This column has three square units. It has a length of three. One, two, three. How many of these columns like this will there be? There'll be one, two, three, four, 'cause our length here at the top is four. So, this time, four times, we will see three square units. One, two, three, and we'll see that one, two, three, four times. So, no matter which of these we solved, whether we counted the square units like in the beginning, or we multiplied the side lengths, the three and the four, in every case, we're gonna find that this equals 12 square units. The area of Rectangle A is 12 square units because it covers 12 square units.
• Why always so confusing
• I am so confused on everything. HELP🤔🤔😕