Decimal Operations: Add, Subtract, Multiply, Divide — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. The pattern is: 0.25, 0.75, 2.25, 6.75. What is the rule?
A) Add 0.50
B) Multiply by 3
C) Multiply by 2
D) Add 1.50
The correct answer is B) Multiply by 3. Each term is three times the previous one (0.25 × 3 = 0.75, 0.75 × 3 = 2.25, 2.25 × 3 = 6.75), confirming the rule.
2. Which operation makes 4.8 become 0.48?
A) Subtract 4.32
B) Divide by 10
C) Multiply by 0.01
D) Divide by 100
The correct answer is B) Divide by 10. Dividing by 10 shifts the decimal one place left, moving 4.8 to 0.48.
3. Jake earned $6.50 per hour for 8 hours, then spent $19.75. How much does he have left?
A) $32.25
B) $33.25
C) $30.25
D) $32.75
The correct answer is A) $32.25. First find total earnings: $6.50 × 8 = $52.00, then subtract spending: $52.00 − $19.75 = $32.25.
4. If n ÷ 0.5 = 14, what is n?
A) 28
B) 7
C) 0.7
D) 2.8
The correct answer is B) 7. Dividing by 0.5 is the same as multiplying by 2, so n must be half of 14: n = 7.
Part B: Fill in the Blank
Write the correct answer on each line.
1. The next number in the pattern 0.5, 1.0, 2.0, 4.0 is 8.0.
The answer is 8.0. Each number doubles the previous one (0.5 × 2 = 1.0, 1.0 × 2 = 2.0, 2.0 × 2 = 4.0), so the next term is 4.0 × 2 = 8.0.
2. 7.2 × 100 ÷ 10 = 72
The answer is 72. Multiplying by 100 shifts the decimal two places right (720), then dividing by 10 shifts it one place left (72).
3. If 0.6 × n = 3.6, then n = 6.
The answer is 6. Divide both sides by 0.6: 3.6 ÷ 0.6 = 6, and you can verify because 0.6 × 6 = 3.6.
4. 15.75 ÷ 2.5 = 6.3
The answer is 6.3. Multiply both by 10 to clear the decimal divisor: 157.5 ÷ 25 = 6.3.
5. (3.5 + 1.5) × (10.0 − 7.5) = 12.5
The answer is 12.5. Solve each set of parentheses first: 3.5 + 1.5 = 5.0 and 10.0 − 7.5 = 2.5, then multiply 5.0 × 2.5 = 12.5.