1. RATIOS and PROPORTIONS REVIEW By: Teachers who care!

2. RATIOS & PROPORTIONS A ratio is a comparison of two numbers by division. To write ratios, use the word to, a colon, or a fraction bar. EXAMPLE #1: John read 3 books in 4 days. Write the ratio of books to days. Words: 3 to 4Colon: 3:4 Fraction: 3/4

3. RATIOS & PROPORTIONS A proportion is a statement that two ratios are equal. EXAMPLE#2: Is a proportion? Find the cross products. 30 = 30 TRUE If TRUE, the statement is a proportion.

4. RATIOS & PROPORTIONS EXAMPLE#3: Is a proportion? Find the cross products. 20 = 21 FALSE If FALSE, the statement is NOT a proportion.

5. RATIOS & PROPORTIONS EXAMPLE#4: Solve the proportion: Find the cross products. 10 Divide both sides by 10.

6. RATIOS & PROPORTIONS There are 5 boys and 6 girls in Grant School. 1. What is the ratio of girls to boys using a fraction? 2. What is the ratio of girls to children in Grant School (use a colon)? 6:11 3. What is the ratio of boys to children in Grant School (use words)? 5 to 11

7. RATIOS & PROPORTIONS Are the following proportions? FALSE – Not a proportion TRUE – this is a proportion

8. RATIOS & PROPORTIONS Find the missing numbers to make the following proportions. 9 10

9. SCALE DRAWINGS A scale drawing is a drawing of an object with dimensions proportional to those of the actual object. To find lengths from scale drawings, set up and solve proportions.

10. SCALE DRAWINGS USING PROPORTIONS EXAMPLE#1: ¼ in = 5 ft is a scale for a rock band’s concert stage. A. The scale length of the drum stand is 1 in. What is the actual length of the drum stand? Cross multiply..25 Divide by.25

11. SCALE DRAWINGS USING PROPORTIONS EXAMPLE#2: ¼ in = 5 ft is a scale for a rock band’s concert stage. B. The actual length of the stage is 60 ft. What is the scale length of the stage? Cross multiply. 5 5 Divide by 5

12. SCALE DRAWINGS USING PROPORTIONS Given a scale of ½ in = 4 ft, find the actual length for each scale length given..5.5