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Can we go on!. You have 5 minutes to complete check-up. Lets Check!. 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.
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Can we go on! You have 5 minutes to complete check-up.
Lets Check! • 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 418-428
Vocabulary • Proportion: is an equation that states that two ratios are equivalent. • 3/5 = 6/10 • This is read “3 is to 5 as 6 is to 10” • Algebra form: • a/b = c/d where b and d are nonzero numbers
Using Equivalent Ratios: • When one of the numbers in a proportion is unknown, you can find the number by solving the proportion.
Use equivalent ratios • A person burns about 210 calories in 30 minutes of skating. About how many calories would the person burn in 60 minutes. • First write yourself a proportion. • 210 calories/30 minutes = C/60 minutes • Ask yourself what can I multiply 30 by to get to 60. • 2 • Because you multiplied the 30 by 2 to get 60, you must multiply the 210 by 2. Which gives you? • 420
Try some • 1/5 = z/20 • 4 • 8/3 = k/18 • 48 • 9/c=3/12 • 36
Solve proportions using algebra • The same method you used to solve division equations can be used to solve proportions with the variable in the numerator. • 6 = x 10 25 Since this is x divide by 25, you must do the opposite. So multiply both sides by 25. So that will give you 150/10 = x 15=x
Try some • 4/14 = m/49 • Multiply both sides by 49 • 14 = m • 25/30 = x/12 • Multiply both side by 12 • 10= x • h/33 = 2/6 • Multiply both side by 33 • h = 11
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. • So use cross products form an equation. • 4 = 10 6 x 6 * 10 = 4*x 60 = 4x solve by dividing both sides by 4 15=x
Try some! • k/27 = 4/6 • 6k=108 divide both sides by 6 • K=18 • 20/16= n/12 • 16n = 240 divide both sides by 16 • n=15
Use cross product to tell if equal • 24/104, 3/13 • Yes • 6/7, 21/18 • No • 3.4/4.3, 5.6/6.5 • No
Practice • Workbook Pages 105-108 evens