Warmup 10/9/13

1. Warmup10/9/13 Spend the first 5 minutes of class each day looking through the homework so you can either help each other or ask Mr. C. to go through a problem on the board as a class. Objective Tonight’s Homework Convert units given only variables pp 317: 1, 2, 3, 4, 7, 30

2. Homework Help Let’s spend the first 10 minutes of class going over any problems with which you need help.

3. Notes on Abstract Rate Problems When talking about rate problems, we need to make sure to keep each item with its proper unit. If we spend x minutes on y activities, we can write it two ways:

4. Notes on Abstract Rate Problems When talking about rate problems, we need to make sure to keep each item with its proper unit. If we spend x minutes on y activities, we can write it two ways: x minutes_ or y activities y activities x minutes The important thing is that we keep each variable with its proper unit.

5. Notes on Abstract Rate Problems When solving problems using rates, we need to do 3 steps: 1) Set up the ratios and equations 2) Add in modifiers 3) Solve for what we want and check units

6. Notes on Abstract Rate Problems Example: Peter purchased p pencils for d dollars. If the p pencils had cost x more dollars, how many pencils could Peter have purchased for $20?

7. Notes on Abstract Rate Problems Example: Peter purchased p pencils for d dollars. If the p pencils had cost x more dollars, how many pencils could Peter have purchased for $20? 1) At the most basic, this question is asking for this: (pencils / dollar) * dollars = pencils

8. Notes on Abstract Rate Problems Example: Peter purchased p pencils for d dollars. If the p pencils had cost x more dollars, how many pencils could Peter have purchased for $20? 1) At the most basic, this question is asking for this: (pencils / dollar) * dollars = total pencils We would set up our equation like this: p pencils * 20 dollars = total pencils d dollars

9. Notes on Abstract Rate Problems 2) Next we need to modify the equation. p pencils * 20 dollars = total pencils d + x dollars We’re being told the pencils cost x more dollars each, so we add in the x with the dollars.

10. Notes on Abstract Rate Problems 3) Last, we can cross out units. Just like we can cross out the same number if it’s on the top and bottom of a fraction, we can do the same with words. p pencils * 20 dollars = total pencils d + xdollars

11. Notes on Abstract Rate Problems 3) Last, we can cross out units. Just like we can cross out the same number if it’s on the top and bottom of a fraction, we can do the same with words. p pencils * 20 dollars = total pencils d + xdollars So how many pencils can we purchase? 20p pencils Double check that d + x the units in the end match what we want!

12. Group Practice Look at the example problems on pages 315-317. Make sure the examples make sense. Work through them with a friend. Then look at the homework tonight and see if there are any problems you think will be hard. Now is the time to ask a friend or the teacher for help!

13. Exit Question #29 If you want to convert something in dollars / year to Euros / hour, you would need to…. a) Multiply by Euros and divide by dollars b) Multiply by dollars and divide by Euros c) Divide by dollars and divide by Euros d) Divide by Euros / dollars, then divide by year / hour e) Multiply by Euros / dollars, then multiply by year / hour f) Give up. This would be too hard.