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Good Afternoon!

Good Afternoon!. Today we will be learning about Adding and subtracting 2 decimal places. Let’s warm up :. Round to the nearest whole number:. 1) 33. 1) 32.78. 2) 4.32. 2) 4. Round to the nearest tenths:. 3) 22.67. 3) 22.7. 4) 7.885. 4) 7.9. Round to the nearest thousandths:.

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Good Afternoon!

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  1. Good Afternoon! Today we will be learning about Adding and subtracting 2 decimal places Let’s warm up : Round to the nearest whole number: 1) 33 1) 32.78 2) 4.32 2) 4 Round to the nearest tenths: 3) 22.67 3) 22.7 4) 7.885 4) 7.9 Round to the nearest thousandths: 5) 8.4568 5) 8.457 CONFIDENTIAL

  2. Review Let’s review what we did in the last session. Estimating, or being able to guess and come close to a correct answer, is an important part of mathematics and a very handy tool for everyday life. Rounding off is a kind of estimating. We can round a decimal number with the help of a number line. Round 3.4 to the nearest whole number. 3.4 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 The number 3.4 is closer to 3 than it is to 4. So, the rounded value of 3.4 is 3. CONFIDENTIAL

  3. Review We can round a decimal number using place value To round off decimals: 1) Find the place value you want (the "rounding digit") and look at the digit just to the right of it. 2) If that digit is less than 5, do not change the rounding digit but drop all digits to the right of it. 3) If that digit is greater than or equal to five, add one to the rounding digit and drop all digits to the right of it. CONFIDENTIAL

  4. Review Round 12.67 to the nearest tenth. STEP 1: Look at the digit in the place to the right of where you want to round. 12.67 STEP 2: If it is less than 5 round down. If it is 5 or greater than 5, round up. 12.7 Round up to 12.7. Hence, the rounded value of 12.67 to the nearest tenth is 12.7. CONFIDENTIAL

  5. Review To round 75.9876 to the nearest hundredths. 1) Find the rounding digit first. 2) This is the "8". We are trying to get rid of the all the digits to the right of the 8, but the result should be as accurate as possible. 75.9876 3) Now look one digit to the right, at the digit in the thousandths place which is “7". 75.9876 4) See that 7 is more than 5, Add one to the rounding digit and change all the rest of the digits to the right of it to zero. so the number "8" is incremented to “9”. 75.99 Hence, the rounded value of 75.9876 to the nearest hundredths is 75.99 CONFIDENTIAL

  6. Let’s get started. Adding 2 decimal places First let us know few key words before we start. ADDEND: It is the number to be added. In 4.6 + 1.3 = 5.9, 4.6 and 1.3 are addends. COMPENSATION: When adding, add a number to one addend and subtract the same number from the other addend to find the sum. • $2.30 + $3.50 • - $0.30 + $0.30 • = $2.00 + $3.80 • = $5.80 Add a number. Subtract the same number. CONFIDENTIAL

  7. We will add the decimal numbers with the help of 10 by 10 grids. Find 1.25 + 1.12. STEP 1: Draw the grids displaying 1.25 + 1.12 The grids display 1.25 The grids display 1.12 CONFIDENTIAL

  8. STEP 2: Put 1.25 and 1.12 together. The pink square shows 1.25 and blue square shows 1.12. STEP 3: Count the total number of shaded squares. 100 + 100 + 37 = 237. 100 squares = 1 37 squares = 0.37 Therefore, the total number of shaded squares is = 2.37. CONFIDENTIAL

  9. We can add the decimal numbers on paper Find 12.45 + 21. 68. STEP 1: Line up the decimal points. 12.45 + 21. 68 Carry STEP 2: Add each place. Regroup if needed. Write the decimal point in the sum. 11 12.45 + 21. 68 34.13 The sum is 34.13 CONFIDENTIAL

  10. We will now learn to estimate the sum of decimal numbers We know that estimateis an answer that is close to the exact answer. Estimate 12.45 + 21.68. We will use rounding to find the estimated value. STEP 1: Rounding each addend to the nearest whole number. 21.68 rounds to 22. 12.45 rounds to 12. CONFIDENTIAL

  11. STEP 2: Add the estimated values of the addends. 12 + 22 34 Hence the estimated value of 12.45 + 21. 68 is 34. Now your turn: 1) Find 36.26 + 16.67 1) 52.93 2) Estimate 36.26 + 16.67 2) 53 CONFIDENTIAL

  12. Subtracting 2 decimal places First let us know few key words before we start. • DIFFERENCE: It is the answer to a subtraction problem. • MINUEND: It is the number from which another number is to be subtracted. • SUBTRAHEND: It is the number to be subtracted from the Minuend. Difference Minuend 7 – 3 = 4 Subtrahend CONFIDENTIAL

  13. We will subtract the decimal numbers with the help of 10 by 10 grids. Find 1.25 - 1.12 STEP 1: Draw the grids displaying 1.25 - 1.12. Color 1 grid completely. Color 25 squares of the second grid. The grids display 1.25 CONFIDENTIAL

  14. STEP 2: Model 1.25 - 1.12 by crossing out all of the first grid and 12 colored squares on the second grid. Count the number of shaded squares that are left. Here 13 squares are left. Hence, the difference is 0.13. CONFIDENTIAL

  15. We can subtract the decimal numbers on paper Find 17.55 - 11. 18. STEP 1: Line up the decimal points. 17.55 - 11. 18 Carry Subtract each place. Regroup if needed. Write the decimal point. STEP 2: 415 17.55 - 11. 18 6.37 The difference is 6.37 CONFIDENTIAL

  16. STEP 3: You can use the inverse relationship between addition and subtraction to check. 1 11. 18 + 6.37 17.55 Find 21.32 - 7. 85. 13.47 CONFIDENTIAL

  17. We will now learn to estimate the difference of decimal numbers Estimate 17.55 - 11. 18. STEP 1: Rounding each addend to the nearest whole number. 17.55 rounds to 18. 11.18 rounds to 11. STEP 2: Subtract the estimated values of the Subtrahend from minuend. 18 - 11 7 Hence the estimated value of 17.55 - 11. 18 is 7. Estimate 21.32 - 7. 85. 13 CONFIDENTIAL

  18. BREAK CONFIDENTIAL

  19. GAME Click on the link below for some exciting puzzle http://www.thekidzpage.com/onlinejigsawpuzzles/kids-jigsaw-puzzles/12-piece-jigsaw/03-27-07-donkey.html CONFIDENTIAL

  20. Assignments Find the value of the following: 1) 3. 11 + 0.36 3) 3. 11 - 0.36 1) 3.47 3) 2.75 2) 44.92 + 21. 37 4) 44.92 - 21. 37 4) 23.55 2) 66.29 CONFIDENTIAL

  21. Estimate the value of the following: 5) 3. 69 + 3.36 7) 7. 27 - 2.87 5) 7 7) 4 6) 5.92 + 7. 37 8) 11.32 - 4. 79 8) 6 6) 13 CONFIDENTIAL

  22. 9) Nancy bought a pencil for $1.24 and an eraser for $0.70. What is the total amount that she had to pay? 9) $1.94 10) Ben bought a bag for $5.70 and a book for $4.25. By what amount the price of bag is more than the book ? 10) $1.45 CONFIDENTIAL

  23. Let’s Review what we did today ADDEND: It is the number to be added. In 4.6 + 1.3 = 5.9, 4.6 and 1.3 are addends. • DIFFERENCE: It is the answer to a subtraction problem. • MINUEND: It is the number from which another number is to be subtracted. • SUBTRAHEND: It is the number to be subtracted from the Minuend. Difference Minuend 7 – 3 = 4 Subtrahend CONFIDENTIAL

  24. Review Find 12.45 + 21. 68. STEP 1: Line up the decimal points. 12.45 + 21. 68 Carry STEP 2: Add each place. Regroup if needed. Write the decimal point in the sum. 11 12.45 + 21. 68 34.13 The sum is 34.13 CONFIDENTIAL

  25. Review Find 17.55 - 11. 18. STEP 1: Line up the decimal points. 17.55 - 11. 18 Carry Subtract each place. Regroup if needed. Write the decimal point. STEP 2: 415 17.55 - 11. 18 6.37 The difference is 6.37 CONFIDENTIAL

  26. Review STEP 3: You can use the inverse relationship between addition and subtraction to check. 1 11. 18 + 6.37 17.55 CONFIDENTIAL

  27. Review Estimate 17.55 - 11. 18. STEP 1: Rounding each addend to the nearest whole number. 17.55 rounds to 18. 11.18 rounds to 11. STEP 2: Subtract the estimated values of the Subtrahend from minuend. 18 - 11 7 Hence the estimated value of 17.55 - 11. 18 is 7. Estimate 21.32 - 7. 85. CONFIDENTIAL The estimate is 13.

  28. You have done a nice job. See you in the next session. CONFIDENTIAL

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