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## Basic geometry and measurement

### Course: Basic geometry and measurement > Unit 1

Lesson 10: Area versus perimeter# Comparing areas word problem

Sal compares the area of two posters using their side-lengths. Created by Sal Khan.

## Want to join the conversation?

- Are there any other ways to calculate area?(26 votes)
- Yes to find the area of a rectangle, multiply its height by its width. For a square you only need to find the length of one of the sides (as each side is the same length) and then multiply this by itself to find the area.(7 votes)

- how to measure a shapes like croissant or star I mean is there a way to measure it in details ?(11 votes)
- With more complex shapes, you're best served by dividing them into more simple forms and simple adding the areas together. A five sided star can be divided into 10 equal, obtuse triangles.(12 votes)

- I still do not understand it! I am getting upset / mad!(10 votes)
- Are there any other ways to calculate area(8 votes)
- What if you were given the area but had to find the perimeter r?(5 votes)
- Do we have to use this way?(4 votes)
- How much is one inch?(3 votes)
- Why does it say I'm wrong if 6 multiplied by one. Is6(2 votes)
- what are the ways to calculate area(3 votes)
- heelooo what do you mean it hard i 4 years olf(2 votes)

## Video transcript

Mary's rectangular poster
is 36 inches by 20 inches. Susan's rectangular poster
is 26 inches by 30 inches. Which poster has a larger area
and by how many square inches? So let's think about these. So this is Mary's poster. Mary's poster is 36
inches by 20 inches. So it's 36 inches by 20 inches. So it might look
something like that. So the area is going to be
36 times 20 square inches. 36 times 2 is 72. So 36 times 20 is going
to be 720 square inches. Now let's think about
Susan's situation. So let's draw Susan's poster. Susan's poster is 26
inches by 30 inches, so 26 inches by 30 inches. So Susan's poster might
look something like that. That's Susan's poster, my best
attempt to draw a rectangle. What's the area here? The area is 26 times
30 square inches, which is equal
to-- let's actually multiply this one
out-- 26 times 30. We could do 26 times 3 and
essentially add a 0 there. So 3 times 6 is 18. 3 times 2 is 6, plus 1 is 78. And actually, I could have
probably done that in my head. 3 times 20 is 60, plus 3
times 6 is 18, gets us 78. But this isn't 3 times 26. 3 times 26 would be 78. 30 times 26 is 780. So it's 780 square inches. So whose poster, which
poster has a larger area? Susan's. Susan's poster
has a larger area. And by how many square inches? Well, hers is 780 square
inches while Mary's is 720 square inches. So it's by 60 square inches. 780 minus 720 would be 60.