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Illustrative Math
Grade 7
Let’s explore the U.S. flag.
Illustrative Math Unit 7.4, Lesson 1 (printable worksheets)
Imagine you have a painting that is 15 feet wide and 5 feet high. To sketch a scaled copy of the painting, the ratio of the width and height of a scaled copy must be equivalent to 15:5. What is the height of a scaled copy that is 2 feet across?
We know that the height is 1/3 the width, so h = 1/3 · 2 or 2/3.
Sometimes ratios include fractions and decimals. We will be working with these kinds of ratios in the next few lessons.
One standard size for the United States flag is 19 feet by 10 feet. On a flag of this size, the union (the blue rectangle in the top-left corner) is 7 5/8 feet by 5 3/8 feet.
There are many places that display flags of different sizes.
Many classrooms display a U.S. flag.
Flags are often displayed on stamps.
There was a flag on the space shuttle.
Astronauts on the Apollo missions had a flag on a shoulder patch.
On a U.S. flag that is 19 feet by 10 feet, the union is 7 5/8 feet by 5 3/8 feet. For each question, first estimate the answer and then compute the actual percentage.
The largest U.S. flag in the world is 225 feet by 505 feet.
Is the ratio of the length to the width equivalent to 1:1.9, the ratio for official government flags?
The ratio of the given flag is 1:505/225 = 1: 2.24
The flag is not in the official ratio of 1:1.9
The area of the flag is 225 · 505 = 113625 square feet = 12625 square yard
It weighs 3322.37 ounces = 207.65 pounds.
The Open Up Resources math curriculum is free to download from the Open Up Resources website and is also available from Illustrative Mathematics.
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