Subtracting Decimals by Partitioning

Subtracting Decimals by Partitioning

Breaking numbers apart to find the difference Year 5 Mathematics Australian Curriculum

WALT (We Are Learning To)

Recap how partitioning helps us add decimals Identify place value in digits up to three decimal places Subtract decimals by breaking them into standard expanded form Use non-standard partitioning when we need to 'regroup' to subtract

Success Criteria

I can break decimal numbers into their place value parts I can subtract each part separately I can combine the results to find the final answer I can identify when I need to regroup using non-standard form

Key Vocabulary

Minuend - The first number in subtraction Subtrahend - The number being subtracted Difference - The result of subtraction Expanded Form - Writing numbers to show place value Partitioning - Breaking numbers into parts

Decimal Place Value Refresh

Match the place value to its description: 1. Thousandths → a) Third digit right of decimal 2. Hundredths → b) Second digit right of decimal 3. Ones → c) Left of decimal point 4. Tenths → d) First digit right of decimal

Standard Partitioning Method

Example: 0.857 - 0.324 Step 1: Partition both numbers 0.857 = 0.8 + 0.05 + 0.007 0.324 = 0.3 + 0.02 + 0.004 Step 2: Subtract each part Step 3: Combine results

Working Through Standard Partitioning

When Standard Partitioning Won't Work

Problem: 0.52 - 0.17 Standard form: 0.52 = 0.5 + 0.02 We can't do 0.02 - 0.07! Solution: Use non-standard partitioning Regroup: 0.52 = 0.4 + 0.12 Now: 0.12 - 0.07 = 0.05

Check Your Understanding

True or False: The number 0.63 can be written as 0.5 + 0.13 Think about it... Discuss with your partner Be ready to explain your reasoning!

Practice and Extension

Guided Practice: 0.74 - 0.28 Independent Practice: 0.91 - 0.46 Extension Challenge: 1.235 - 0.678 Differentiation: Use place value charts for support Advanced: Create your own decimal subtraction problems