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Lesson 3: Area of rectangles with fractional side lengths

# Finding area with fractional sides 1

Learn how to calculate the area of rectangles with fractional side lengths. Watch examples of this concept in action and practice applying it to different problems. The video emphasizes understanding the process, not just getting the answer.

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• I STILL DONT GET IT they lose me at when they did the squares
• Sal showed 2 ways to figure out the area or the square

1): multiplying the width and height

2): is to take the numerator(the top number) of each fraction, and use that to make a grid.
Example: 5/9 is the height so top to bottom Sal separated the area into 5 sections
after doing that with height and width it made a grid each square being 1/9 by 1/8

He figured out the area by multiplying 1/9 by 1/8 (Which is 1/72)

then sal figured out the number of squares by multiplying the number top to bottom then left to right (height by width) that being 7x5(35)

and at the very end multiplied the number of squares (35)by the area or each squares(1/72) that is 35/72

(The thing about meters squared is just a poor example you don't have to understand it)
• When you are multiplying the height and width are you finding the area or the perimeter?
• You are finding the area width*height=Area
Perimeter=2*width+2*height
• I don't understand the relationship of 8 and 9.
7x5 seems logic however where did you get 8/9 from?
• The 9 from the 5/9 and the 8 form the 7/8
• clarify why you split the rectangle into 35 equal parts. It seems random. Please point out that you are using the numerators of both fractions to divide it into equal parts and why.
• Because of the following reason:
Let us pretend this is an addition
You can't do 7/8 + 5/9. The denominators are different. So you will find the MCP. The same is with multiplication.

• how ado you times a fraction by a normal number
• lets just say 3x 1/10, you would convert it into 3/1. 3/1 x 1/10 is 3/10.
(1 vote)
• This is the death of fifth graders LOL☠
• The death of me more like
• Guys, He said seconds instead of meters!

• At why does it have to be 35 rectangles? Its very random in my opinion.
• Hi Austin!

It has to be 35 squares because that's the total amount of squares in the rectangle's area if you count each one on the screen. Each square has the same size/area of measurement and they distribute evenly (by "filling") the rectangle with no gaps or variations of size within the rectangle. Keeping each square the same size allows us to create a fraction that is from consistently measured data. If each square is consistently the same size then we know the fraction we create representing the total amount of squares (the 35 of 35/72) will be consistent and true as well.

You could also think of it as 7 columns of squares of 5 rows of squares = 35 total squares, or 5 rows of squares by 7 seven columns of squares = 35 total squares.

If anyone has another perspective with which to answer this question with, please feel free to add it.
(1 vote)
• Your method does not work with the problem I have
(1 vote)
• Why don't you try asking a question related to the problem that you have? Someone many be able to show you if the method does work or offer an alternate method.