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Course: Geometry (OPS pilot) > Unit 1
Lesson 7: Perimeter, circumference, and area- Find a missing side length when given perimeter
- Find perimeter when a side length is missing
- Perimeter word problem: tables
- Perimeter word problem: skating rink
- Perimeter word problems
- Area & perimeter word problem: dog pen
- Area & perimeter word problem: table
- Comparing areas word problem
- Area and perimeter situations
- Represent rectangle measurements
- Area & perimeter of rectangles word problems
- Decomposing shapes to find area: grids
- Understand decomposing figures to find area
- Decomposing shapes to find area: add
- Decomposing shapes to find area: subtract
- Decompose figures to find area
- Drawing a quadrilateral on the coordinate plane example
- Drawing polygons with coordinates
- Area of a parallelogram on the coordinate plane
- Area and perimeter on the coordinate plane
- Coordinates of a missing vertex
- Example of shapes on a coordinate plane
- Dimensions of a rectangle from coordinates
- Coordinates of rectangle example
- Quadrilateral problems on the coordinate plane
- Quadrilateral problems on the coordinate plane
- Parallelogram on the coordinate plane
- Radius, diameter, circumference & π
- Labeling parts of a circle
- Radius, diameter, & circumference
- Radius and diameter
- Radius & diameter from circumference
- Relating circumference and area
- Circumference of a circle
- Area of a circle
- Area of a circle
- Partial circle area and arc length
- Circumference of parts of circles
- Area of parts of circles
- Circumference review
- Area of circles review
- Finding circumference of a circle when given the area
- Area of a shaded region
- Impact of increasing the radius
- Circumference and rotations
- Area and circumference of circles challenge
- Shaded areas
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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?(28 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.(8 votes)
- how to measure a shapes like croissant or star I mean is there a way to measure it in details ?(10 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.(16 votes)
- I still do not understand it! I am getting upset / mad!(11 votes)
- I am terrible at area and perimeter too(3 votes)
- Are there any other ways to calculate area(7 votes)
- What if you were given the area but had to find the perimeter r?(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)
- Guess the movie by emojis 🍎💀📒(3 votes)
- How much is one inch?(2 votes)
- One inch equals 2 an a half centimeters look at a ruler if you don’t believe me.(1 vote)
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.