Upload
rosemary-quinn
View
245
Download
0
Tags:
Embed Size (px)
Citation preview
Operations with Decimals!
Adding and Subtracting DecimalsHow is adding and subtracting decimals similar to adding and subtracting whole
numbers?
Activities 1-3 – See handout
• Is there a relationship between adding and subtracting decimals and adding and subtracting whole numbers?
• When in the real world would you add and subtract decimals?
Steps for adding and subtracting
• Write the numbers down vertically.• Line up the decimal points. • Bring the decimal point straight down.• Add and subtract as you would whole
numbers.
Examples
• Add 8.13 and 2.76. 8.13 +2.76
• Add 1.459 + 23.7 1.459 + 23.7___
Examples
• Subtract 5.508 – 3.174.
5.508 - 3.174
• Subtract 21.9 – 1.605. 21.900 - 1.605
Real – Life Application
$3.45 $10.00+$3.90 - ______
Your turn
• Complete with your clock partner and then get your answers checked by me.
• 4.206 + 10.85 =
• 27.9 – 0.905 =
Conclusion
• How is adding and subtracting decimals similar to adding and subtracting whole numbers?
Multiplying Decimals
How is multiplying decimals similar to and different from multiplying whole
numbers?
Activity – Multiplying Decimals by Decimals
• Complete Activity (pages 7 and 8)• What conjecture can you make about the
relationships between multiplying decimals and multiplying whole numbers?
Steps to Multiplying Decimals
• Multiply as you would with whole numbers. • Count the number of decimal places in the
decimal factor. • The product has the same number of decimal
places.
Examples
• It is helpful to estimate to see if your answer is reasonable!
• Find 6 x 3.91
• Find 3 x 0.0016.
Examples
• Multiply 4.8 x 7.2.
• Multiply 3.1 x 0.05.
Real Life Application
• You buy 2.5 pounds of tomatoes. You hand the cashier a $10 bill. How much change should you receive?
Conclusion
• How is multiplying decimals similar to and different from multiplying whole numbers?
Dividing Decimals
How can you model decimal division with pattern blocks and numbers?
Complete Activity 1 on Division Modeling
• Dividing decimals by whole numbers– Place the decimal point in the quotient above the
decimal point in the dividend.– Then divide as you would with whole numbers.
– Find 7.6 ÷ 4 Find 36.4 ÷ 2
Dividing Decimals by Decimals
• Multiply the divisor and dividend by a power of ten to make the divisor a whole number.
• Place the decimal point in the quotient and divide as you would with whole numbers.
Examples
• Find 18.2 ÷ 1.4.
• Find 9.6 ÷ 1.2
• Find 0.459 ÷ 0.51
Real – World Example
Summary
• How can you model decimal division with pattern blocks and numbers?
• How else can you divide if you don’t draw or use a model?