Can we go on!

You have 5 minutes to complete check-up.

Lets Check!1. 8 to 52. 4 to 193. 6 to 234. 16 to 10 and 24 to 155. 75meter/30sec. 2.5m/sec6. $8.75 per scarf7. Danny8. 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 25Since this is x divide by 25, you must do the opposite. So multiply both sides by 25.So that will give you 150/10 = x15=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 x6 * 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