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Can we go on! You have 5 minutes to complete check-up. Lets Check! 1. 2. 3. 4. 5. 6. 7. 8. 8 to 5 4 to 19 6 to 23 16 to 10 and 24 to 15 75meter/30sec. 2.5m/sec $8.75 per scarf Danny 12 men Writing and Solving Proportions • I can write and solve proportions using ratios and algebra. • Textbook Pages 412-416 Vocabulary • Proportion: is an equation that shows that two ratios are equivalent. Ratio: 2 of 3 rows Ratio: 8 of 12 dots Proportion : 2/3 = 8/12 Cross Products • Cross Product: when you multiply the numerator of each ratio by the denominator of the other ratio. • The cross products of proportions are equal to each other. To see if two ratios form a proportion, check to see if the cross products are equal: 8 20 10 25 so multiply 25 time 8 and 10 time 20 What you get is 200=200 Try some Are these proportions: 10/16 = 5/8 Yes 3/8 = 15/40 Yes 3/5=12/18 No Solving Using Mental Math: • When one of the numbers in a proportion is unknown, you can find the number by solving the proportion. • Just ask yourself what did they do to one to get the other. • 4 = 20 12 x Multiply by 5 X= 60 Try some • • • • • • 1/5 = z/20 4 8/3 = k/18 48 9/c=3/12 36 Review • Can someone remind me how we solve multiplication equations: • We divide both sides by whatever number is with the variable. • 3x = 18 • Divide both sides by 3 • X=6 Solving using equations: • You can solve proportions by using cross product and making an equation. • You cross multiply then solve for the variable. • 10 50 60 x Cross multiply. 10x = 3000 Solve by dividing both sides by 10 X=300 You try some! • 91/x = 7/5 • 7x= 455 X=65 24/36 = 10/x 24x=360 X= 15 9/6 = h/14 6h=126 H=21 Practice • Workbook Pages 105-106 odds