Adding, Subtracting, Multiplying, and Dividing Decimals: A Complete Review

Welcome to The ultimate guide for anyone who needs a refresher on how to work with decimals. Whether you are watching In this video, I show you almost everything there is to know about decimal operations, or you prefer a written walkthrough, this article covers every step you need to master adding, subtracting, multiplying, and dividing decimals.

What Is a Decimal?

A decimal is a number that uses a base‑10 place value system, with a decimal point separating the whole‑number part from the fractional part. For example, 4.27 has a whole part of 4 and a fractional part of .27, which represents 27 hundredths. Understanding the position of each digit is the foundation for all four operations.

Adding Decimals

Adding decimals is similar to adding whole numbers, but you must keep the decimal points aligned.

  1. Line up the decimal points. Write the numbers one under the other so that each column of digits represents the same place value.
  2. Fill in missing zeros. If one number has fewer digits after the decimal, add zeros to the right (e.g., 3.5 becomes 3.50).
  3. Add column by column. Start from the rightmost digit, carry over when the sum exceeds 9, and keep the decimal point in the same column in the answer.

Example:

7.84 + 2.5 ------- 10.34

Subtracting Decimals

The subtraction process mirrors addition.

  1. Align the decimal points.
  2. Pad the shorter number with zeros if necessary.
  3. Subtract column by column, borrowing when a digit in the top number is smaller than the one below it.

Example:

9.60 - 3.27 ------- 6.33

Multiplying Decimals

Multiplication requires a two‑step approach: multiply as if the numbers were whole, then place the decimal point correctly.

  1. Ignore the decimal points. Multiply the numbers as whole numbers.
  2. Count total decimal places. Add the number of digits to the right of the decimal in each factor.
  3. Insert the decimal point. In the product, count the total decimal places from the right and place the point there.

Example:

3.2 × 0.45 32 × 45 = 1440 Total decimal places = 1 (from 3.2) + 2 (from 0.45) = 3 Result = 1.440

Dividing Decimals

Division is easiest when the divisor becomes a whole number.

  1. Make the divisor a whole number. Move the decimal point to the right until the divisor has no fractional part.
  2. Move the dividend the same number of places. This keeps the value of the fraction unchanged.
  3. Divide as usual. Perform long division or use a calculator, then place the decimal point in the quotient.

Example:

5.76 ÷ 0.12 Move decimal two places: 5.76 → 576, 0.12 → 12 576 ÷ 12 = 48 Result = 48.0

Common Mistakes & Quick Tips

Practice Problems

Try these problems to reinforce each operation. Write your answers on paper before checking the solutions.

  1. Add: 4.375 + 2.6
  2. Subtract: 9.04 – 3.718
  3. Multiply: 1.25 × 0.32
  4. Divide: 7.2 ÷ 0.4

Answers:

Where to Learn More

Welcome to A Review of Decimals with Mr. J! Need a refresher on how to handle decimals in everyday math? Visit mathantics.com for free video lessons, interactive quizzes, and printable worksheets. The site’s “Decimals” playlist includes a video titled “Adding, Subtracting, Multiplying, Dividing Decimals” that walks through each step with clear visuals.

Conclusion

Mastering decimal operations is essential for success in algebra, finance, science, and daily life. By aligning decimal points, counting places accurately, and converting divisors when needed, you can solve any decimal problem with confidence. Keep practicing the examples above, explore the free resources at mathantics.com, and soon the four operations will feel as natural as working with whole numbers.