Road Trip! Using Multiplication and Division of Decimals

1. Road Trip!Using Multiplication and Division of Decimals

2. Javier is planning a road trip from Houston to El Paso with three friends. All agree to equally split the cost of the trip. Your job will be to help Javier organize his budget for the trip.

3. Review of Decimal Multiplication We will use an easy 3 step process to help refresh our memory. Let us consider the example, 8.2 X 5

4. Step 1 Count the number of digits to the right of the decimal point. One number to the right of the decimal point. 8.2 X 5

5. Step 2 • Multiply like there was no decimal (we moved it to the right to get whole numbers) 8 2 X 5 41 0

6. Step 3 • Use the number of digits you counted in Step 1 to place the decimal back where it belongs • We counted 1 digit in Step 1, so we move the decimal point by 1 place to theleft 410 = 410.0 41 0 0 . .

7. 8.2 82 16.482 164.82 Before We Begin: Review Decimal Division Multiply both the divisor and dividend by the smallest power of 10 that is needed for the divisor to be a whole number. Remember if we multiply both the dividend and the divisor by 10 it does change our answer… ½ * 10/10 = 10/20 = ½!!!!

8. 82 164.82 2 . 0 1 Now, Divide like normal: For Example, -164 0 8 - 0 8 2 - 82 0

9. Problem 1 • The distance between the two cities is 822.5 miles. • Javier wants to calculate how much money he should expect to spend for gas during his trip. • Javier’s car uses 32.9 miles per gallon. • How many gallons will his car consume for a roundtrip?

10. What do we want to know? 1) We want to know how many gallons of gas the trip will take! And what information did we get??? 2) The distance was 822.5 miles And they got 32.9 miles per gallon How are we going to set the problem up????? Miles ____________ = GALLONS!!! Miles Per Gallon 822.5 ÷ 32.9

11. What about for the Roundtrip? To find the total gallons used for a roundtrip we can multiply by 2. 25 x 2= 50 gallons

12. Problem 2 • The hotel room Javier plans to stay at costs $132.30 a night and will accommodate all 4 friends. • How much would each person spend on the hotel for one night? • See if you can do 2) on your own………

13. What did we need to do this time? We take the cost and divide by 4!!! We get $132.30 ÷ 4 = $33.075

14. Problem 3 • Javier and his friends plan to go out for pizza one night. • The cost of a pizza is $16.84. • How much would each person pay if one of the friends doesn’t attend? _ A = 5.613

15. Problem 4 • On one day Javier is planning to go to a rock concert and plans to pay for two of his friend’s admission. • Tickets are $36.50, how much would Javier spend on tickets? Answer: $109.50

16. Problem 5 • Javier remembers that he has to get a new tire for his car before leaving, which costs $46.49. • He also needs an oil change that costs $17.95. • He has a coupon for 25% off his total purchase. • What is the total after the discount?

17. Set it Up… $64.44 • The total cost is ________ • If we take 25% off, we have 75% left… 100%-25% = 75% • Try it two ways: • Find 25% of the total cost and subtract it from the total cost, or • Take .75 (because we convert the % to a decimal) and multiply by the total cost! Answer: $48.33