7th grade · Math · Unit 2 of 17
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.
Maine Learning Results learning standard: 7.NS.A.2; 7.EE.B.3 · computing with decimals and solving multi-step problems with 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 Maine
In the Maine Learning Results, this is unit 2 of 17 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.
Source: Maine Department of Education
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
Which is the best estimate for 80.3 × 3.1?
- 83
- 24
- 2400
- 240
240
Hint: Round each number to a friendly one: 80.3 ≈ 80 and 3.1 ≈ 3. Then 80 × 3 = 240.
Question 2
What is 24.5 − 5.71?
24.5 − 5.71 = ?
answer box
18.79
Hint: Line up the decimal points and fill in zeros so both numbers have the same places: 24.50 − 5.71. Subtract, regrouping where you need to: 18.79.
Question 3
Apples cost $1.70 per kilogram. How much do 4.6 kg of apples cost, in dollars?
answer box
7.82
Hint: Multiply the price by the mass: 1.7 × 4.6. Without decimals that's 17 × 46 = 782; there are 2 decimal places in total, so the cost is $7.82.
Question 4
What is 8 ÷ 0.8?
8 ÷ 0.8 = ?
answer box
10
Hint: Multiply both numbers by 10 so you divide by a whole number: 80 ÷ 8 = 10.
Question 5
What is 5.8 × 0.6?
5.8 × 0.6 = ?
- 0.0348
- 34.8
- 0.348
- 3.48
3.48
Hint: Multiply as if there were no decimal points: 58 × 6 = 348. The factors have 2 decimal places in total, so the product does too: 3.48.
Question 6
What is 20.91 + 22.9?
20.91 + 22.9 = ?
answer box
43.81
Hint: Line up the decimal points and give every number two decimal places: 20.91 + 22.90. Add column by column: 43.81.