Decimal Operations: Add, Subtract, Multiply, Divide — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Which is the best estimate for 7.83 × 4.12?
A) 24
B) 28
C) 32
D) 36
The correct answer is C) 32. Rounding 7.83 to 8 and 4.12 to 4 gives 8 × 4 = 32, which is the closest estimate to the exact product of 32.26.
2. What is 0.36 ÷ 0.04?
A) 0.9
B) 9
C) 90
D) 0.09
The correct answer is B) 9. Multiply both numbers by 100 to remove decimals: 36 ÷ 4 = 9.
3. Evaluate: 5.4 + 2.6 × 1.5
A) 9.3
B) 12.0
C) 9.0
D) 8.1
The correct answer is A) 9.3. Order of operations requires multiplying first: 2.6 × 1.5 = 3.9, then adding 5.4 + 3.9 = 9.3.
4. A store sells 2.5 kg bags of rice for $4.80 each. What is the cost per kilogram?
A) $1.82
B) $1.92
C) $2.40
D) $1.60
The correct answer is B) $1.92. Divide $4.80 by 2.5 kg: multiply both by 10 to get 48 ÷ 25 = 1.92 dollars per kilogram.
Part B: Fill in the Blank
Write the correct answer on each line.
1. 0.8 × 0.25 + 1.6 = 1.8
The answer is 1.8. Multiply first: 0.8 × 0.25 = 0.2, then add 0.2 + 1.6 = 1.8 following order of operations.
2. 16.8 ÷ 0.4 = 42
The answer is 42. Multiply both numbers by 10 to eliminate the decimal divisor: 168 ÷ 4 = 42.
3. If 3 items cost $8.67 total, each item costs $2.89.
The answer is $2.89. Divide 867 cents by 3 to get 289 cents, which equals $2.89 per item.
4. The best estimate for 49.6 ÷ 4.8 is about 10.
The answer is 10. Rounding 49.6 to 50 and 4.8 to 5 gives 50 ÷ 5 = 10, a clean estimate near the exact quotient.
5. 2.5 × 3.2 − 4.0 = 4.0
The answer is 4.0. Multiply first: 2.5 × 3.2 = 8.0, then subtract 8.0 − 4.0 = 4.0.