WEEK 7 MID TERM REVIEW HALF LESSON
WEEK 8 SCALE DRAWING
Since it is not always possible to draw on paper the actual size of real-life objects such as the real size of a car, an airplane, we need scale drawings to represent the size like the one you see below of a van.
In real-life, the length of this van may measure 240 inches. However, the length of a copy or print paper that you could use to draw this van is a little bit less than 12 inchesSince 240/12 = 20, you will need about 20 sheets of copy paper to draw the length of the actual size of the vanIn order to use just one sheet, you could then use 1 inch on your drawing to represent 20 inches on the real-life objectYou can write this situation as 1:20 or 1/20 or 1 to 20Notice that the first number always refers to the length of the drawing on paper and the second number refers to the length of real-life objectExample #1:Suppose a problem tells you that the length of a vehicle is drawn to scale. The scale of the drawing is 1:20If the length of the drawing of the vehicle on paper is 12 inches, how long is the vehicle in real life?Set up a proportion that will look like this:
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Do a cross product by multiplying the numerator of one fraction by the denominator of the other fractionWe get : Length of drawing × 20 = Real length × 1Since length of drawing = 12, we get:12 × 20 = Real length × 1240 inches = Real lengthExample #2:The scale drawing of this tree is 1:500If the height of the tree on paper is 20 inches, what is the height of the tree in real life?
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Set up a proportion like this:
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Do a cross product by multiplying the numerator of one fraction by the denominator of the other fractionWe get : Height of drawing × 500 = Real height × 1Since height of drawing = 20, we get:20 × 500 = Real length × 110000 inches = Real height