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Welcome to this IRSC Adult Education Live Virtual Lesson
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  1. Welcome to this IRSC Adult Education Live Virtual Lesson Diana Lenartiene, Ed. S. moderator/instructor

  2. Introducing… your virtual classroom Elluminate Meeting/Classroom

  3. Respond to poll Emoticons Chat Adjust volume

  4. Elluminate Meeting/Classroom

  5. Elluminate Meeting/Classroom

  6. Elluminate Meeting/Classroom

  7. Adding and Subtracting Decimals Solve problems involving addition and subtraction of decimals.

  8. We will now watch a video on adding and subtracting with decimals

  9. To add decimals • Line up the decimal points and add the columns from right to left. • Place a decimal point in the answer directly below the other decimal points.

  10. Example 1 0.64 + 0.39 Line up the decimal points. 0.64 + 0.39 __________________________ Add the columns. 0.64 + 0.39 __________________________ 1.03

  11. Example 2 5.74 + 3.3 Line up the decimal points. 5.74 + 3.3 _____________________________ Add the columns. 5.74 + 3.3 _____________________________ 9.04

  12. Try this one on your own! 39.66 +22.7 Remember, • line up the decimals, • Place the decimal point in the answer under the ones in the problem, • Add like whole numbers.

  13. Answer 11 39.66 +22.7 62.36

  14. To subtract decimals • Line up the decimal points. • Subtract the columns from right to left, regrouping if necessary. • Place a decimal point in the answer directly below the other decimal points.

  15. Example 1 0.86 – 0.49 Line up the decimal points 0.86 - 0.49 __________________________ Regroup the tenths. Subtract the columns. 0.86 - 0.49 __________________________ 16 7 0.37

  16. We will now watch a video on multiplying with decimals

  17. BOOK NOTE Multiplying Decimals 0.7 You can use graph paper to model decimal multiplication. Here is a model of the product of0.7and0.3. 0.3 1 Because 21 of the 100 squares are shaded, 0.70.3 = 0.21. 1 Multiplying Decimals Words Multiply decimals as you would whole numbers. Then place the decimal point in the product. The number of decimal places in the product is equal to the sum of the number of decimal places in the factors. 0.70.3 = 0.21 Numbers

  18. Multiplying Decimals  + ––– –––––– 1 EXAMPLE Multiplying Decimals 5.82 2 decimal places 0.41 2 decimal places 582 2328 ––––––– 4 decimal places 2.3862 3 1 2 4

  19. Multiplying Decimals 6 0.4 Checking Reasonableness To check that the product in Example 1 is reasonable, round each factor to the place value of the leading digit, then multiply. The leading digit of a number is the first nonzero digit. 5.82 Round to the nearest whole number. 0.41 Round to the nearest tenth. Because 6 0.4 = 2.4, the product of the previous example is reasonable.

  20. Multiplying Decimals  + ––– –––––– CHECK After you place the decimal point, you can drop any zeros at the end of an answer. 2 EXAMPLE Multiplying Decimals 6.45 2 decimal places 18 0 decimal places 5160 645 –––––– 116.10 2 decimal places ANSWER 6.45  18 = 116.1 Because 6  20 = 120, the product is reasonable.

  21. Multiplying Decimals   + + ––– ––– –––––– ––––––– CHECK Write a zero before the 7 as a placeholder so that the number has 5 decimal places. After you place the decimal point, you can drop any zeros at the end of an answer. 2 EXAMPLE Multiplying Decimals 1.273 3 decimal places 6.45 2 decimal places 0.06 2 decimal places 18 0 decimal places 5160 0.0 7638 5 decimal places 645 –––––– 116.10 2 decimal places ANSWER ANSWER 6.45  18 = 116.1 1.273  0.06 = 0.07638 CHECK Because 6  20 = 120, the product is reasonable. Because 1  0.06 = 0.06, the product is reasonable.

  22. Multiplying Decimals 3 EXAMPLE Multiplying Decimals to Find Area Central Park Central Park is a rectangular park about 2.5 miles long and about 0.5 mile wide. What is the area of Central Park? SOLUTION A = lw Write formula for area of a rectangle. = l w 2.5 (0.5) Substitute 2.5 for l and 0.5 for w. = 1.25 Multiply. ANSWER The area of Central Park is about 1.25 square miles.

  23. Now, you need to make a copy of this screen to send to your teacher for proof of Attendance. This can be done in three easy steps:

  24. If you still have questions, please contact me at: dlenarti@irsc.edu Thank you for viewing this presentation. Diana Lenartiene, IRSC ABE Instructor