4-3 Equivalent Ratios and Proportions:

4-3 Classwork: WORKBOOK, page 175 Problems 7 through 12 You have 20 minutes to complete.

4-4 Solving Proportions

1 2 __=__ 2 4 2*2=41*4=4 1 x ____ = ____ 2 4 2x = 4 x=2 Remember how we solved ratios to see if they were proportionate? Cross multiplying is always the best choice: If a value is missing, we still do the same thing, cross multiply and solve for the missing amount: Divide both sides by 2

Now take the amount you solved and put it in place of the x: 1x

Let’s Practice 6=36 ____ 10 x Cross Multiply

6 * x = 6x 10 * 36 = 360

6x = 360 Divide both sides by 6.

x = 60

Now check your answer: x1060 If you cross multiply, you would have 360

Your turn: 4 x ___ = ___ 36180

Don’t forget that you can ALWAYS reduce a fraction!!

4/36 will reduce down….but to what? Divide by 2…..4 2 = = 18 But 2/18 can be further reduced…again, divide by 2 to become 1/9. Now use 1/9 in the proportion.

1 x x 180 x 20

Checking your answer: 4 = x *180 = 720 x*36 = 36x 720 = 36x 20 = x

You can use proportions to solve real world problems. If you have 3 binders that are all the same size and they take up 4 inches on a shelf, how much shelf space would you need if you have 26 binders?

Start by setting up your first ratio: Binders3 Shelf space4”

Then we use the same “set up” for the other ratio: Binders26 Shelf Space x

Make one proportion: Binders: 326 Shelf Space4 x

326 4 x 3x104 x 34 2/3”

Homework: 1) 7 63 ___ =___ x 54 2) 24 x ___ = ___ ) 840 ___ = ___ 9x

Carmen bought 3 pounds of peanuts for $1.08. Her friend also bought peanuts but spent $1.80. How many pounds of peanuts did her friend buy?