Decimals
Decimals are another way to write fractions whose denominators are powers of 10. 0.3 = 3/10, 0.47 = 47/100. Every place to the right of the decimal point is ten times smaller: tenths, hundredths, thousandths. Decimals are everywhere — money, measurements, science.
Key Concepts
Place Value with Decimals
In 3.745: 3 is ones, 7 is tenths (7/10), 4 is hundredths (4/100), 5 is thousandths (5/1000). Reading: 'three and seven hundred forty-five thousandths.' When comparing, line up the decimal points and compare digit by digit from left to right.
Adding and Subtracting Decimals
Line up the decimal points. Add zeros as placeholders if needed. Then add or subtract as normal whole numbers, keeping the decimal point in the same column. 12.5 + 3.47 = 12.50 + 3.47 = 15.97.
Multiplying and Dividing Decimals
To multiply: ignore decimals, multiply as whole numbers, then count total decimal places in both factors and place the point that many places from the right. 2.4 × 1.5 = 24×15=360, two decimal places → 3.60. To divide by a decimal: move both decimal points right until the divisor is a whole number.
🆕 Decimal Place Value Explorer
Enter a decimal to see its place value breakdown.
✅ Check Your Understanding
1. In 4.27, which digit is in the hundredths place?
2. To add decimals, you must first...
3. 2.4 × 1.5 = ?