Decimals

Virginia Standard Breakdown

Students will learn how to estimate, solve, and explain problems using addition, subtraction, multiplication, and division with decimals. They’ll work with both single-step and multi-step problems.

Students will be able to

Make a good estimate before solving to check if their answer makes sense.
Add, subtract, multiply, and divide decimals.
Solve word problems that use decimals (like money or measurements).
Explain how they solved the problem and why their answer is reasonable.

When Will I ever use this?

💵 Money & Shopping

Add up prices when you’re buying snacks or clothes.
Estimate the total before you get to the checkout.
Figure out how much change you should get.

🍪 Cooking & Baking

Measure ingredients like 0.5 cups of sugar.
Double or cut recipes in half.

📏 Measuring Stuff

Use a ruler or tape measure (like 3.75 inches).
Track your height - Can you ride the roller coaster at Kings DOminion
Read numbers on science experiments.

🏀 Sports & Fitness

Time your laps (like 5.25 minutes).
Keep up with batting averages or shooting percentages.
Measure how far you throw or run.

🎮 Everyday Life & Fun

Estimate how long your phone battery will last (35.5%).
Split a pizza bill with friends or family.

Rounding Decimals to the nearest whole number

Find the whole-number part (the number left of the decimal).
Look at the tenths digit (the first digit after the decimal).
Decide:
- Tenths 0–4 → round down (whole number stays).
- Tenths 5–9 → round up (add 1 to the whole number).
Write the rounded answer (no decimal needed).

Example : 3.2 → tenths = 2 → round down → 3 8.76 → tenths = 7 → round up → 9

Adding Decimals

Line up the decimal points — write the numbers vertically so the decimal points are one under the other.
Add zeros so both numbers have the same number of digits after the decimal (e.g., 1.4 → 1.40).
Add from right to left, just like whole numbers. Add hundredths, then tenths, then the ones — carry when needed.
Put the decimal point in the answer directly under the other decimal points.
Check with estimation (round each number and add) to see if your answer is reasonable.

Subtracting Decimals

Line up the decimal points. Write the numbers vertically with the decimals one under the other.
Add zeros so both numbers have the same number of digits after the decimal (e.g., 4.8 → 4.80).
Subtract right to left (start with the smallest place value).
Borrow if needed: if a digit is too small to subtract from, borrow from the next column to the left — this may mean borrowing from the ones place into the tenths, then from tenths into hundredths, etc.
Place the decimal point in the answer directly under the other decimal points.
Check your work by adding the answer to the number you subtracted (the subtrahend). The sum should equal the original first number (the minuend).

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