Decimal Operations: Add, Subtract, Multiply, Divide — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. What is 3.6 × 2.5 − 4.2?
A) 4.8
B) 5.8
C) 4.6
D) 5.4
3.6 × 2.5 = 9.0. Then 9.0 − 4.2 = 4.8.
2. Evaluate: (12.4 − 7.8) + 2.5 × 3
A) 12.1
B) 14.6
C) 11.1
D) 12.6
Following order of operations: 2.5 × 3 = 7.5 first. Then (12.4 − 7.8) = 4.6. Finally 4.6 + 7.5 = 12.1.
3. A number divided by 4 equals 3.75. What is the number multiplied by 2?
A) 15
B) 7.5
C) 30
D) 22.5
If n ÷ 4 = 3.75, then n = 3.75 × 4 = 15. Then 15 × 2 = 30.
4. Which expression equals 6.25?
A) 2.5 × 2.5
B) 12.5 ÷ 3
C) 3.1 + 3.05
D) 1.25 × 4
2.5 × 2.5 = 6.25. Check others: 12.5÷3≈4.17; 3.1+3.05=6.15; 1.25×4=5.0. Only 2.5×2.5=6.25.
Part B: Fill in the Blank
Write the correct answer on each line.
1. (4.8 + 3.2) × 0.5 = 4.0
(4.8 + 3.2) = 8.0. Then 8.0 × 0.5 = 4.0.
2. 18.6 ÷ 3 − 2.45 = 3.75
18.6 ÷ 3 = 6.2. Then 6.2 − 2.45 = 3.75.
3. 0.25 × 8 + 1.6 ÷ 4 = 2.4
0.25 × 8 = 2.0. 1.6 ÷ 4 = 0.4. Sum = 2.0 + 0.4 = 2.4.
4. If n × 0.6 = 4.2, then n = 7.
n = 4.2 ÷ 0.6 = 7. Check: 7 × 0.6 = 4.2 ✓.
5. 5.5 × 4 − 12.8 ÷ 2 = 15.6
5.5 × 4 = 22.0. 12.8 ÷ 2 = 6.4. Then 22.0 − 6.4 = 15.6.