Measuring the sides of a rectangle to find area
About this video
The narrator measures the sides of a rectangle with a centimeter ruler, being careful to start at zero. The sides are 7 cm and 8 cm, and the opposite sides match. Multiplying the side lengths gives an area of 56 square centimeters.
You'll be able to
- measure a side length with a ruler, starting at zero.
- find the area of a rectangle by multiplying its two side lengths.
- give area in square units, like square centimeters.
Key words
- area
- How much flat space a shape covers, measured in square units.
- rectangle
- A four-sided shape with square corners where opposite sides are the same length.
- side length
- How long one side of a shape is.
- square centimeters
- The unit for area when the sides are measured in centimeters.
Transcript
- [Narrator] So my goal here is to find the area of this rectangle right over here and we can assume it is a rectangle. And so to figure that out, we just have to take two of the side lengths. For example, this side length here, we have to figure out what that is.
And if then if we figure out this side length, then if we were to multiply them, then we would get the area. Now how do we figure out those side lengths? Well, I luckily have a ruler right over here. So let's see. This side length over here. And I wanna be very careful.
I wanna start my ruler right at the beginning, right at zero. Some people make the mistake of trying to start at one or at some other number. No, you can't start anywhere. You have to start right at the beginning. So I'm starting, you could think of that as zero before I get to one.
And it looks like I go one, two, three, four, five, six centi- Seven centimeters. Let me be careful. One, two, three, four, five, six, seven centimeters in that direction. So let me write that down. Seven centimeters. And if I measured this other side, this is a rectangle, it should be the same.
And yes, that one also is seven centimeters. And now this length over here, it looks like it is. And once again, I'm starting at zero. One, two, three, four, five, six, seven, eight centimeters. So this is eight centimeters. And so this one up here should be eight centimeters if this is really a rectangle.
And we see that it is. So now I've done the measurements and I can figure out the area. It's just going to be this side length, times this side length. So let's see, if I took seven centimeters times eight centimeters. 7 X 8 = 56 square, square centimeters Centimeters.
And we are done.
Video © Khan Academy, used under CC BY-NC-SA. Watch on Khan Academy. Puzzicle is not affiliated with Khan Academy.