Decimals (Tenths and Hundredths) • Topic 3 of 3

Add and Subtract Decimals

The most important rule for adding/subtracting decimals: ALWAYS line up the decimal points!

Column Method Steps:

  • Write numbers with decimal points aligned
  • Add zeros to make same number of decimal places
  • Add or subtract from RIGHT to LEFT (like whole numbers)
  • Bring the decimal point STRAIGHT DOWN into the answer
  • Carry or borrow just like with whole numbers
Adding Decimals: 4.25 + 0.75 = 5.004.25+ 0.755.00Hundredths: 5+5=10, write 0 carry 1Tenths: 2+7+1=10, write 0 carry 1Ones: 4+0+1=5Decimal point goes straight down4.25 + 0.75 = 5.00
Solved Examples
1
Worked Example
Add 4.25 + 0.75.
SolutionLine up decimals: 4.25 + 0.75. Hundredths: 5+5=10 (write 0, carry 1). Tenths: 2+7+1=10 (write 0, carry 1). Ones: 4+0+1=5. Answer: 5.00 = 5.
2
Worked Example
Subtract 1.35 from 3.8.
SolutionWrite 3.8 as 3.80. Hundredths: 0-5 (borrow): 10-5=5. Tenths: 7-3=4. Ones: 3-1=2. Answer: 2.45.
3
Worked Example
Riya bought a notebook for Rs.25.50 and a pen for Rs.12.75. She paid Rs.50. How much change?
SolutionTotal cost: 25.50 + 12.75 = 38.25. Change: 50.00 - 38.25 = 11.75. Answer: Rs.11.75 change.

Key Points

  • ALWAYS line up decimal points — this is the most important rule
  • Add zeros to make all decimals have the same number of places
  • Carry and borrow exactly as you would with whole numbers
  • Bring the decimal point straight down into the answer
Quick Check — 4 MCQs
Tap an option to check your answer0 / 4
Q1.To add or subtract decimals, line up the:
Explanation: Decimal points.
Q2.$0.5+0.3=$
Explanation: $0.8$.
Q3.$0.7-0.2=$
Explanation: $0.5$.
Q4.$0.25+0.25=$
Explanation: $0.5$.
Practice more MCQs → 📝 Assignment · 35 marks