decimals worksheets addition and subtraction

Teaching Notes

Practice focus: decimals worksheets addition and subtraction. Focus: Mixed Decimal Addition and Subtraction. Use the worked example and teaching sequence below to explain the reasoning before independent practice.

Before You Begin

• Identify addition, subtraction, multiplication, and division.

Teaching Steps for Parents and Teachers

1. Line up decimal points so that ones, tenths, and hundredths match.
2. Add trailing zeros if they help you see the places; this does not change a number.
3. Add from the smallest place shown and regroup as needed.
4. Put the decimal point in the sum directly below the other decimal points.
5. Align the decimal points and write equivalent trailing zeros when needed.
6. Subtract from the smallest place.
7. An exchange from one place gives ten units of the place immediately to its right, just as in whole-number subtraction.
8. Keep the decimal point aligned in the difference.

Worked Examples

Evaluate 1.25+0.6.

1. Align the decimal points so corresponding places line up.
2. Use trailing zeros if needed, then calculate one place at a time.
3. 1.25 + 0.6 = 1.85

Answer: 1.85

Evaluate 2.4-0.75.

1. Align the decimal points so corresponding places line up.
2. Use trailing zeros if needed, then calculate one place at a time.
3. 2.4 − 0.75 = 1.65

Answer: 1.65

Common Mistakes and How to Help

Align decimal points, not the right-hand ends of the numbers. For example, a tenth must not be added to a hundredth merely because both digits happen to be last.

Subtract either addend from the sum. Estimate with nearby whole numbers to check the size of the answer.

Adding a zero at the end of a decimal is allowed; moving its decimal point is not. Remember to reduce the place from which you exchanged one unit.

Add the difference to the amount subtracted. Compare the total with the original decimal.

Questions to Check Understanding

• Which operation must be completed first, and why?
• Which step explains your answer?
• Can you apply the same reasoning when the numbers change?

Practice Advice

Work through the example together. Ask the learner to explain the first two problems, then try three independently. Review the first incorrect step before assigning more practice.

Next Practice

• Use New Numbers to practice the same skill with different values.
• If the learner needs help, return to the example and model each step before trying again.