🔢 Decimal Operations
Line up the decimal points before adding or subtracting
▶ Play Door 6Adding & Subtracting Decimals
To add or subtract decimals, line up the decimal points so that tenths sit under tenths and hundredths under hundredths. Fill empty places with zeros if it helps, then add or subtract as usual and bring the decimal point straight down.
Worked example
Problem: Add 1.2 + 0.35.
- Line up points (1.20 + 0.35) = 1.55.
Answer: Line up points (1.20 + 0.35) = 1.55.
Multiplying Decimals & Powers of 10
Multiplying or dividing by 10, 100, 1000 just moves the decimal point: ×10 moves it one place right, ÷10 moves it one place left.
To multiply a decimal by a whole number, multiply as normal, then place the decimal point so the answer has the same number of decimal places as the decimal you started with.
Worked example
Problem: What is 0.5 × 10?
- Move the point one place right → 5.
Answer: Move the point one place right → 5.