Decimal Operations
Calculate with decimals
Start with the basics and progress through 3 lessons. Each lesson builds on the previous one.
0 of 3 lessons done
Test Your Knowledge
10 questions, new mix each time (from 45)
In This Topic (3 lessons)
Adding and Subtracting Decimals
Learn how to add and subtract decimal numbers by lining up the decimal points.
Multiplying Decimals
Learn how to multiply decimal numbers using place value strategies and the standard algorithm.
Dividing Decimals
Learn how to divide decimal numbers using place value understanding and the standard algorithm.
Performing arithmetic with decimal numbers requires attention to decimal point placement. In addition and subtraction, you align the decimal points vertically, ensuring that digits of the same place value are combined. In multiplication, you count total decimal places in both factors to position the decimal point in the product. Division may require moving decimal points to work with whole numbers.
These operations appear constantly in real life: calculating grocery totals, adjusting recipes, computing gas mileage, and managing finances. Mastering decimal operations gives you confidence in handling precise calculations that whole numbers cannot express.
What You'll Learn
- Add and subtract decimals by aligning decimal points
- Multiply decimals and correctly place the decimal point
- Divide decimals including by decimal divisors
- Estimate results to check decimal calculations
- Solve multi-step word problems involving decimals
Frequently Asked Questions
Why do we align decimal points when adding?
Aligning decimal points ensures we add digits with the same place value: tenths with tenths, hundredths with hundredths. Without alignment, we would incorrectly combine different-sized pieces.
How do I know where to put the decimal point in multiplication?
Count the total decimal places in both numbers being multiplied. The answer has that many decimal places. For 2.5 × 1.4, there are 2 decimal places total, so 3.50.
What if I need to divide by a decimal?
Multiply both the divisor and dividend by a power of 10 to make the divisor a whole number. For example, 4.5 ÷ 0.9 becomes 45 ÷ 9 = 5.