Scale Drawing/Scale Models Scale Drawings & Models are used to represent objects that are too large or too small to be drawn or built at actual size Examples: RC Cars, Atlas, Insects… others?

Scale Gives the ratio that compares the measurements of the drawing or model to the measurements of the real object. They are proportional. ex. – map scale

You try it… Find the actual distance if the map scale is 4 inches = 30 miles 2 inches = x = 15 miles Use CMAD (cross multiply and divide) to solve this proportion. First, multiply 2 inches and 30 miles for a product of 60. Then, divide 60 by 4 for a quotient of 15. Note: students will get the same answer if they first simplify 4 inches : 30 miles to 2 inches : 15 miles before they CMAD.

How can you use this? A scale drawing of a rectangular room has a length of 6 inches and a width of 4 inches. The drawing uses a scale of one inch to three feet. 1. How many square feet is the room? 2. How much will it cost to carpet the room if carpeting costs $5.50 per square foot? There are two methods for solving problem #1. Students could either convert the measurements from the scale drawing into the actual dimensions of a length of 18 feet and a width of 12 feet, then use the formula for finding the area of a rectangle (A=lw) to find the area, or they could square the scale and find that the scale of the area of the rectangle is 1 sq in : 9 sq ft, then set the scale equal to the ratio of the area of the scale drawing (6 inches x 4 inches = 24 sq in). Either process will give the answer as 216 square feet. Using the price of $5.50 per square foot, the answer to #2 is $1,188. 216 ft2 216 ft2 x $5.50 = $1,188

What do they look like? REPLICA (an exact copy of the original) REDUCTION (from original to smaller) ENLARGEMENT (from original to larger)

What’s the difference? SCALE SCALE FACTOR Gives a ratio that compares measurements Does not have to be in the same units EX 1 inch : 5 feet It’s a scale, but it must have the same units, and is in simplest form You might have to convert the units EX 1 inch : 5 feet (scale) CONVERT both to inches ; 1 inch : 60 inches = 1:60 scale factor SCALE SCALE FACTOR