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Chapter 2

Chapter 2. Multiplying and Dividing Decimals. 2-1 Multiplication Properties. IWBAT use multiplication properties to solve problems mentally. Multiplication Properties. Examples. Find mentally. 1) Choose a property. Distributive. 2) Use the property. 3) Order of operations. 30 + 21.

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Chapter 2

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  1. Chapter 2 Multiplying and Dividing Decimals

  2. 2-1 Multiplication Properties IWBAT use multiplication properties to solve problems mentally.

  3. Multiplication Properties

  4. Examples Find mentally 1) Choose a property Distributive 2) Use the property 3) Order of operations 30 + 21 51 Find 1) Choose a property Commutative 2) Use the property 3) Order of operations = 3860

  5. Examples Find mentally 1) Choose a property Distributive 2) Use the property 3) Order of operations 2400 - 8 2392 Find mentally 1) Choose a property Zero Property 2) Use the property 0

  6. Practice Identify and use the multiplication property to solve the problems mentally. • 1

  7. 2-2 Multiplying Whole Numbers and Decimals IWBAT multiply large whole numbers and decimals

  8. Multiplying Whole Numbers 1) Write vertically, lining up the digits in the ones place 26,328 15 ______ 2) Multiply by the ones 26,328 15 ______ 131640 3) Use a placeholder and then multiply by the ten 26,328 15 ______ 131640 26328X

  9. Continued . . . 4) Add 26,328 15 ______ 131640 26328X _______ 394,920

  10. Examples 209 36 1,650 412 399 705 ____ ______ ______ 1254 3300 1995 327X + ______ 1650X 000X + ______ 3524 2793XX + ______ 19800 281,295

  11. Multiplying Decimals Find 1.0894.2 1) Multiply just like whole numbers 1.08 94.2 ______ 216 432X 972XX + ______ 101736 2) Count the number of places after a decimal in the problem 3 digits 3) Start right and move the number of places 101.736

  12. Examples 1) 42.7 2.1 2) 0.38 86 0.38 86 42.7 2.1 ______ ______ 228 427 304X 854X + _______ + ______ 3268 8967 32.86 89.67

  13. Practice 1) 399 2) 52.7 3) 417 705 3.9 26 4) 2.637 5) 5.03 4.36 0.07 6) 5.76 4.08 7) 0.08 0.007 __________ __________ __________ __________ __________

  14. 2-3 Interpret the Remainder IWBAT interpret quotients and remainders in division problems

  15. Example #1 You and your 10 friends are going on a field trip to an amusement park. You can only enter the ride in groups of four. You decide that your friends need to find 5 more classmates to be able to all get in at one time. 1) If you don’t find 5 more people, how many people cannot go in with you? How do you know? 3 people. 11 4 = 2 R3 2) Explain how you decided that you needed 5 more people. 11 + 5 = 16. 16 is divisible by 4. 3) What is the fewest number of people who need to join your group so that you all can go in? How do you know? One person. 11 + 1 = 12. 12 is divisible by 4.

  16. Example #2 Your class is going to see a movie. There are 27 students and your teacher wants one parent for every group of 4 students. Your teacher will go with the remaining students. 1) How many parents will your teacher need? How did you figure it out? 27 4 = 6 R3 6 Parents 2) What does the remainder represent? The number of students in the teacher’s group 3) How many groups will see the show? Explain. 7 groups. There are 6 parent-led groups and one teacher-led group.

  17. Practice Your class of 37 students are taking a boat ride around a lake. Each boat holds 6 people. There are groups of 5 students for each parent. The teacher will be with the remaining students. 1) How many boats are needed? How did you find out? 2) How many students are in the teacher’s group?

  18. 2-4 Dividing by Whole Numbers IWBAT divide whole numbers by whole number divisors

  19. Vocabulary Quotient Divisor Dividend

  20. Vocabulary Divisor Quotient Dividend

  21. Two-Digit Divisor and Whole Number Dividend =? *Divide *Multiply *Subtract *Compare *Bring Down 1) Rewrite as long division and divide the hundreds 2 3 - ____ 3 2 2) Divide the tens *Compare *Divide *Multiply *Subtract *Bring Down 2 3 - ____ 32 23 - ____ 92

  22. 3) Divide the ones *Divide *Multiply *Subtract *Compare *Write remainder, if any 2 3 - _____ 32 - ____ 23 92 92 - ____ 0

  23. 2-5 Dividing a Decimal by a Decimal IWBAT divide decimals by decimals

  24. Dividing decimals by decimals is just like dividing any other number but you have to move the decimals if there is a decimal in the divisor.

  25. 2-6 Work Backwards IWBAT solve problems by working backwards

  26. Example Kim bought 10 ears of corn, one quart of berries, and some tomatoes. Use the data given above. If Kim, gave the cashier $10.00 and received $1.80 in change, how many pounds of tomatoes did Kim buy? 1) Start with what is given and work your way backwards $10.00 - $1.80 $8.20 2) Find amounts that are given to you Corn: 5 for $1.00 10 for $2.00

  27. Money spent on corn and berries: $2.00 + $2.00 $4.00 3) Continue to work backwards $8.20 – $4.00 $4.20 = price of tomatoes 4) Find last part of problem Tomatoes: $1.20 per lb $4.20 $1.20 3.5 lbs of tomatoes

  28. 2-7 Solving Multiplication and Division Equations IWBAT solve multiplication and division equations

  29. 2-8 Using a Pictograph IWBAT use pictographs to solve problems

  30. Remember • Always look at the key first!

  31. Examples 1) How many hours does Bob study each week? 9 hours 2) How many more hours did Roberto study than Maria? Roberto: 8 hours Maria: 1 hour 8 – 1 7 hours

  32. Examples Continued 1) Which year did Middlebury’s population double from it’s original population in 1941? 2) Which year did Middlebury see the biggest increase in population? 1971 and 2001 1961

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