1. CONFIDENTIAL1 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) 32.78 2) 4.32 Round to the nearest tenths: 3) 22.67 4) 7.885 Round to the nearest thousandths: 5) 8.4568

2. CONFIDENTIAL2 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. 00.51.01.52.02.53.03.54.04.55.0 3.4 Round 3.4 to the nearest whole number. The number 3.4 is closer to 3 than it is to 4. So, the rounded value of 3.4 is 3. Review

3. CONFIDENTIAL3 We can round a decimal number using place value 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. 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. Review

4. CONFIDENTIAL4 Round 12.67 to the nearest tenth. Look at the digit in the place to the right of where you want to round. STEP 1: 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. Review

5. CONFIDENTIAL5 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. 3) Now look one digit to the right, at the digit in the thousandths place which is “7". 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”. 75.9876 75.99 Hence, the rounded value of 75.9876 to the nearest hundredths is 75.99

6. CONFIDENTIAL6 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.

7. CONFIDENTIAL7 Find 1.25 + 1.12. We will add the decimal numbers with the help of 10 by 10 grids. STEP 1: The grids display 1.25 The grids display 1.12 Draw the grids displaying 1.25 + 1.12

8. CONFIDENTIAL8 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 = 137 squares = 0.37 Therefore, the total number of shaded squares is = 2.37.

9. CONFIDENTIAL9 We can add the decimal numbers on paper Find 12.45 + 21. 68. STEP 1: STEP 2: 12.45 + 21. 68 Line up the decimal points. 12.45 + 21. 68 Add each place. Regroup if needed. Write the decimal point in the sum. 1 11 1 34.13 Carry The sum is 34.13

10. CONFIDENTIAL10 We will now learn to estimate the sum of decimal numbers We know that estimate is 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. 12.45 rounds to 12. 21.68 rounds to 22.

11. CONFIDENTIAL11 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 2) Estimate 36.26 + 16.67

12. CONFIDENTIAL12 Subtracting 2 decimal places First let us know few key words before we start.  MINUEND: It is the number from which another number is to be subtracted.  DIFFERENCE: It is the answer to a subtraction problem.  SUBTRAHEND: It is the number to be subtracted from the Minuend. 7 – 3 = 4Minuend Difference Subtrahend

13. CONFIDENTIAL13 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

14. CONFIDENTIAL14 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.

15. CONFIDENTIAL15 We can subtract the decimal numbers on paper Find 17.55 - 11. 18. STEP 1: STEP 2: 17.55 - 11. 18 Line up the decimal points. Subtract each place. Regroup if needed. Write the decimal point. 4 15 6.37 Carry The difference is 6.37 17.55 - 11. 18

16. CONFIDENTIAL16 STEP 3: You can use the inverse relationship between addition and subtraction to check. + 6.37 17.55 11. 18 1 Find 21.32 - 7. 85.

17. CONFIDENTIAL17 We will now learn to estimate the difference of decimal numbers STEP 1: Rounding each addend to the nearest whole number. 17.55 rounds to 18. 11.18 rounds to 11. Estimate 17.55 - 11. 18. 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.

18. CONFIDENTIAL18 BREAK

19. CONFIDENTIAL19 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

20. CONFIDENTIAL20 Assignments Find the value of the following: 1) 3. 11 + 0.36 2) 44.92 + 21. 374) 44.92 - 21. 37 3) 3. 11 - 0.36

21. CONFIDENTIAL21 Estimate the value of the following: 5) 3. 69 + 3.36 6) 5.92 + 7. 378) 11.32 - 4. 79 7) 7. 27 - 2.87

22. CONFIDENTIAL22 9) Nancy bought a pencil for $1.24 and an eraser for $0.70. What is the total amount that she had to pay? 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 ?

23. CONFIDENTIAL23 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.  MINUEND: It is the number from which another number is to be subtracted.  DIFFERENCE: It is the answer to a subtraction problem.  SUBTRAHEND: It is the number to be subtracted from the Minuend. 7 – 3 = 4Minuend Difference Subtrahend

24. CONFIDENTIAL24 Find 12.45 + 21. 68. STEP 1: STEP 2: 12.45 + 21. 68 Line up the decimal points. 12.45 + 21. 68 Add each place. Regroup if needed. Write the decimal point in the sum. 1 11 1 34.13 Carry The sum is 34.13 Review

25. CONFIDENTIAL25 Review Find 17.55 - 11. 18. STEP 1: STEP 2: 17.55 - 11. 18 Line up the decimal points. Subtract each place. Regroup if needed. Write the decimal point. 4 15 6.37 Carry The difference is 6.37 17.55 - 11. 18

26. CONFIDENTIAL26 STEP 3: You can use the inverse relationship between addition and subtraction to check. + 6.37 17.55 11. 18 1 Review

27. CONFIDENTIAL27 STEP 1: Rounding each addend to the nearest whole number. 17.55 rounds to 18. 11.18 rounds to 11. Estimate 17.55 - 11. 18. 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. Review

28. CONFIDENTIAL28 You have done a nice job. See you in the next session.