7th grade · Math · Unit 2 of 15
Decimal Operations
Add, subtract, multiply, divide decimals
What your child practices
All four operations with decimals, estimating to check answers, ordering decimals, and money problems such as unit prices.
Minnesota K-12 Academic Standards benchmark: 7.3.5.6 · computing with positive and negative rational numbers
How we explain it
Children can open this short lesson before they practice.
- To add or subtract, line up the decimal points.
- Fill empty places with zeros so the numbers match.
- Then add or subtract like whole numbers.
Example: 3.45 + 2.8 = ? Write 2.8 as 2.80 and line up the points. 3.45 + 2.80 = 6.25. Answer: 6.25
Decimal Operations in Minnesota
In the Minnesota K-12 Academic Standards, this is unit 2 of 15 in 7th grade Math, after Add & Subtract Integers and before Fractions, Decimals & Percents.
Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
What is 8.7 − 1.06?
8.7 − 1.06 = ?
answer box
7.64
Hint: Line up the decimal points and fill in zeros so both numbers have the same places: 8.70 − 1.06. Subtract, regrouping where you need to: 7.64.
Question 2
What is 6.5 × 0.8?
6.5 × 0.8 = ?
- 0.52
- 0.052
- 5.2
- 52
5.2
Hint: Multiply as if there were no decimal points: 65 × 8 = 520. The factors have 2 decimal places in total, so the product does too: 5.20 = 5.2.
Question 3
Put these decimals in order from least to greatest.
- 0.48
- 0.048
- 0.804
- 0.08
- 0.8
0.048 → 0.08 → 0.48 → 0.8 → 0.804
Hint: Compare tenths first, then hundredths, then thousandths. Writing them with the same number of places helps: 0.048, 0.080, 0.480, 0.800, 0.804.
Question 4
Apples cost $5.40 per kilogram. How much do 1.8 kg of apples cost, in dollars?
answer box
9.72
Hint: Multiply the price by the mass: 5.4 × 1.8. Without decimals that's 54 × 18 = 972; there are 2 decimal places in total, so the cost is $9.72.
Question 5
What is 24.17 + 20.5?
24.17 + 20.5 = ?
answer box
44.67
Hint: Line up the decimal points and give every number two decimal places: 24.17 + 20.50. Add column by column: 44.67.
Question 6
Which is the best estimate for 90.3 × 3.1?
- 93
- 270
- 2700
- 27
270
Hint: Round each number to a friendly one: 90.3 ≈ 90 and 3.1 ≈ 3. Then 90 × 3 = 270.