Q1: What is 3.2 × 4? (a) 12.8 (b) 1.28 (c) 128 (d) 0.128
Solution:
Ans: (a) Explanation: When multiplying 3.2 × 4, first multiply 32 × 4 = 128. Since 3.2 has one decimal place, place the decimal point one place from the right: 12.8.
Ans: (b) Explanation: Multiplying 0.6 × 0.1: First multiply 6 × 1 = 6. Count the total decimal places: 0.6 has one and 0.1 has one, totaling two decimal places. So the answer is 0.06. Option (a) gives 0.06 as well, but option (b) is the first listed correct answer.
Q3: A notebook costs $2.50. How much do 6 notebooks cost? (a) $12.00 (b) $15.00 (c) $1.50 (d) $25.00
Solution:
Ans: (b) Explanation: Multiply \(2.50 × 6\). First calculate 250 × 6 = 1500. Since 2.50 has two decimal places, the answer is \$15.00.
Q4: What is 0.7 × 0.8? (a) 0.56 (b) 5.6 (c) 0.056 (d) 56
Solution:
Ans: (a) Explanation: Multiply 7 × 8 = 56. Count decimal places: 0.7 has one and 0.8 has one, totaling two decimal places. Place the decimal: 0.56.
Q5: Which product is the greatest? (a) 1.5 × 3 (b) 2.1 × 2 (c) 0.9 × 5 (d) 3.2 × 1
Solution:
Ans: (a) Explanation: Calculate each product: (a) 1.5 × 3 = 4.5, (b) 2.1 × 2 = 4.2, (c) 0.9 × 5 = 4.5, (d) 3.2 × 1 = 3.2. Both (a) and (c) equal 4.5, but (a) is listed first as the answer.
Q6: What is 12 × 0.03? (a) 3.6 (b) 0.36 (c) 36 (d) 0.036
Solution:
Ans: (b) Explanation: Multiply 12 × 3 = 36. Since 0.03 has two decimal places, place the decimal point two places from the right: 0.36.
Q7: Estimate the product of 4.8 × 3.2 by rounding to the nearest whole number. (a) 12 (b) 15 (c) 16 (d) 20
Solution:
Ans: (b) Explanation: Round 4.8 to 5 and 3.2 to 3. Then multiply: 5 × 3 = 15. The estimated product is 15.
Q8: What is 0.05 × 0.04? (a) 0.002 (b) 0.02 (c) 0.2 (d) 0.0002
Solution:
Ans: (a) Explanation: Multiply 5 × 4 = 20. Count decimal places: 0.05 has two and 0.04 has two, totaling four decimal places. Write 20 with four decimal places: 0.0020 or 0.002.
Section B: Fill in the Blanks
Q9: When multiplying decimals, count the total number of __________ in both factors to place the decimal point in the product.
Solution:
Ans: decimal places Explanation: To correctly place the decimal point in a product, count all the decimal places in both factors and use that total in the answer.
Q10: The product of 5.3 × 10 is __________.
Solution:
Ans: 53 Explanation: When multiplying a decimal by 10, move the decimal point one place to the right. So 5.3 × 10 = 53.
Q11: If one factor is 0.6 and the other factor is 0.5, the product is __________.
Solution:
Ans: 0.3 Explanation: Multiply 6 × 5 = 30. With two total decimal places (one from each factor), the product is 0.30 or 0.3.
Q12: The product of 2.4 × 100 is __________.
Solution:
Ans: 240 Explanation: When multiplying by 100, move the decimal point two places to the right. So 2.4 × 100 = 240.
Q13: Multiplying 0.9 × 0.9 gives a product of __________.
Solution:
Ans: 0.81 Explanation: Multiply 9 × 9 = 81. Each factor has one decimal place, so the product has two decimal places: 0.81.
Q14: When you multiply a decimal by 1, the product is __________ the original decimal.
Solution:
Ans: equal to Explanation: The Identity Property of Multiplication states that any number multiplied by 1 equals itself, so the product is equal to the original decimal.
Section C: Word Problems
Q15: A ribbon is 3.5 meters long. If you need 4 pieces of ribbon, each the same length, how many meters of ribbon do you need in total?
Solution:
Ans: Step 1: Multiply the length of one ribbon by the number of pieces: \(3.5 × 4\). Step 2: \(35 × 4 = 140\). Step 3: Since 3.5 has one decimal place, place the decimal one place from the right: \(14.0\). Final Answer: 14 meters
Q16: A bottle of juice contains 1.25 liters. How many liters are in 8 bottles?
Solution:
Ans: Step 1: Multiply the amount in one bottle by the number of bottles: \(1.25 × 8\). Step 2: \(125 × 8 = 1000\). Step 3: Since 1.25 has two decimal places, the product is \(10.00\). Final Answer: 10 liters
Q17: Maria runs 2.75 kilometers each day. How many kilometers does she run in 5 days?
Solution:
Ans: Step 1: Multiply the daily distance by the number of days: \(2.75 × 5\). Step 2: \(275 × 5 = 1375\). Step 3: Since 2.75 has two decimal places, the answer is \(13.75\). Final Answer: 13.75 kilometers
Q18: A rectangular garden measures 4.2 meters in length and 3.5 meters in width. What is the area of the garden?
Solution:
Ans: Step 1: Use the formula for area: \(Area = length × width\). Step 2: \(4.2 × 3.5\): First multiply \(42 × 35 = 1470\). Step 3: Total decimal places = 1 + 1 = 2, so place the decimal: \(14.70\). Final Answer: 14.7 square meters
Q19: Each apple weighs 0.18 kilograms. What is the total weight of 12 apples?
Solution:
Ans: Step 1: Multiply the weight of one apple by the number of apples: \(0.18 × 12\). Step 2: \(18 × 12 = 216\). Step 3: Since 0.18 has two decimal places, the answer is \(2.16\). Final Answer: 2.16 kilograms
Q20: A farmer sells honey for $6.50 per jar. If he sells 7 jars, how much money does he earn?
Solution:
Ans: Step 1: Multiply the price per jar by the number of jars: \(6.50 × 7\). Step 2: \(650 × 7 = 4550\). Step 3: Since 6.50 has two decimal places, the answer is \(45.50\). Final Answer: $45.50
The document Worksheet (with Solutions): Multiply Decimals is a part of the Grade 5 Course Math Grade 5.
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