I CAN UNDERSTAND RATIOS and PROPORTIONS In this lesson you will use ratios and proportions in order to draw actual objects onto a paper. Architects uses ratio to draw blueprints to scale so builders can understand them. Engineers uses ratios to test structural and mechanical systems for capacity and safety. Who uses Ratios? Ratios are used in technical drawings and blueprints. Ratios is a comparison of two numbers in the SAME UNIT Ratios provide an easy way to compare two quantities. There are 4 possible ways to write a Ratio 4 : 10 4 to 104 girls to 10 boys Lets Practice. Step 2: 6 can be divide into both numbers Solution: 6 inches : 1 inches 6 : 1 Lets continue Problem #1 3 feet : 6 inches Rewritten 36 inches : 6 inches Lets Practice some more Problem #2 24 inches : 4 feet Is the same as 2 feet : 4 feet Step 2: Two can be divide into both numbers Solution: 2/2 feet : 4/2 feet 1 : 2 Continue Scale Reads: 1/4 : 1 If the actual dimensions measures 13 inches by 9 inches, what are the dimensions on your paper? Blueprint Drawing ? 9 13 Scale Reads: 1/4 : 1 If the actual dimensions measures 13 inches by 9 inches, what are the dimensions on your paper? (13 inches) (0.25)= 3.25 inches (9 inches) (0.25)= 2.25 inches Continue Blueprint Drawing So now the Blueprint Drawing is 2.25 3.25 9 13 Scale Reads: 1/2 : 1 If the drawing dimensions measures 6.5 inches by 4.5 inches on paper, What are the actual dimensions? We can also work backwards 4.5 6.5 ?? Continue on a Blueprint Drawing? You should now have a 8 1/2 x 11 graph paper. Please write your name at the bottom 1) Paper should be orientate in Portrait. 2) We will begin drawing our first object. Your scale is 1/4 : 1 Draw three rectangle shape a) 13 x 9 b) 10 x 6 c) 6 x 4 Start here You will need to be convert these numbers to fit the paper. Scale is 1/4 : 1 Three rectangle shape a) 13 x 9 b) 10 x 6 c) 6 x 4 Start here Your Drawing should look similar to this. a) 13 x 9 (bottom) Your Drawing should look similar to this. b) 10 x 6 (middle) Remember: You will need to be convert these numbers to fit the paper. c) 6 x 4 (top) Remember: You will need to be convert these numbers to fit the paper. Your Drawing should look similar to this. Rectangular dowels Drawing Dowels on the top right side of your paper. Top & Side View (8) typical 1x 4 Additional Height Information Drawing 2-D Congratulations you are now ready to draw this picture into a 3D software. In this lesson you have learned to use ratios and proportions in order to draw actual objects onto a paper.