Decimal Operations with Integers
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Decimal Operations with Integers
Adding, Subtracting, Multiplying and Dividing Decimals Year 8 Mathematics Working with Positive and Negative Numbers
What Are Decimals?
Numbers that include a decimal point Represent parts of a whole Can be positive or negative Examples: 3.5, -2.8, 0.25, -10.75
Adding Decimals
Line up decimal points vertically Add zeros if needed for equal decimal places Add from right to left Keep the decimal point in the same position
Practice: Adding Decimals
Solve: 4.6 + 2.35 Solve: -3.7 + 1.25 Solve: 8.9 + (-5.4) Check your decimal point alignment!
Subtracting Decimals
Line up decimal points vertically Add zeros if needed Subtract from right to left Borrow from the next column when needed
Multiplying Decimals
Multiply as if they were whole numbers Count total decimal places in both numbers Place decimal point in the answer Example: 2.3 × 1.5 = 3.45 (2 decimal places total)
Quick Check: Multiplication
What is 0.4 × 0.3? How many decimal places should your answer have? Is the answer positive or negative?
Dividing Decimals
Move decimal point in divisor to make it whole Move decimal point in dividend the same number of places Divide as normal Place decimal point directly above in quotient
Positive vs Negative Decimal Operations
{"left":"Positive + Positive = Positive\nNegative + Negative = Negative\nPositive × Positive = Positive\nNegative × Negative = Positive","right":"Positive - Negative = Positive\nNegative - Positive = Negative\nPositive × Negative = Negative\nNegative ÷ Positive = Negative"}
Mixed Practice Challenge
Calculate: -2.5 + 3.7 Calculate: 4.2 × (-1.5) Calculate: -8.4 ÷ 2.1 Calculate: 5.8 - (-2.3)