**Multiplication by Powers of 10:**
• Multiply by 10 → add 1 zero (4 × 10 = 40)
• Multiply by 100 → add 2 zeros (3 × 100 = 300)
• Multiply by 1,000 → add 3 zeros (2 × 1,000 = 2,000)
**Commutative Property:** Numbers can be multiplied in any order. 8 × 5 = 5 × 8 = 40
**Doubling and Halving Method:** Double one number, halve the other, multiply. Works best with 5 and 25.
• Example: 18 × 5 = 9 × 10 = 90
**Nearest Multiple Strategy:** Round to nearest 10/100, multiply, then add/subtract difference.
• Example: 4 × 19 = 4 × 20 − 4 = 80 − 4 = 76
• Example: 14 × 21 = 14 × 20 + 14 = 280 + 14 = 294
**Breaking into Parts:** Split a number and add products.
• Example: 18 × 5 = (10 × 5) + (8 × 5) = 50 + 40 = 90
**Diagrams to Remember:** Place value table showing how digits shift left when multiplying by 10, 100, 1,000.
**Don't Confuse:** Multiplying by 10 (add one zero) is different from adding 10 (so 4 × 10 = 40, not 14).
Q1. What is 7 × 10?
Answer: A — When multiplying by 10, add one zero to the number, so 7 × 10 = 70.
Q2. Which statement shows the Commutative Property?
Answer: A — The Commutative Property of multiplication means the order of numbers doesn't change the answer.
Q3. How many zeros will be added when 5 is multiplied by 100?
Answer: B — When multiplying by 100, we add two zeros, so 5 × 100 = 500.
Q4. Solve using Doubling and Halving: 16 × 5 = ?
Answer: B — Half of 16 is 8, and 8 × 10 = 80, so 16 × 5 = 80.
Q5. A dairy farm packs 12 pouches in each box. How many pouches are in 10 boxes?
Answer: C — 12 × 10 = 120 pouches (when multiplying by 10, add one zero).
Q6. Use Nearest Multiple to find 3 × 19
Answer: B — 3 × 20 = 60, then subtract 3 × 1 = 3, so 60 − 3 = 57.
Q7. Which multiplication problem is the same as 6 × 14?
Answer: B — By Commutative Property, 6 × 14 = 14 × 6 because the order doesn't change the answer.
Q8. Priya jogs 4 km every day. In 100 days, how many km will she jog?
Answer: B — 4 × 100 = 400 km (when multiplying by 100, add two zeros).
Q9. If you multiply 8 by 1,000, how many zeros will the answer have?
Answer: C — 8 × 1,000 = 8,000, which has three zeros after the 8.
Q10. A school auditorium has 35 rows with 42 seats in each row. Which method works best to find total seats?
Answer: D — All three strategies (breaking into parts, doubling and halving, and nearest multiple) can be used flexibly to find 35 × 42.
What happens when you multiply any number by 10?
The number becomes 10 times larger and we add one zero to the right of the number.
What is the Commutative Property of Multiplication?
The order of numbers in multiplication doesn't matter — 6 × 13 equals 13 × 6.
How do you multiply by 100?
Add two zeros to the right of the number, or the number becomes 100 times larger.
What is the Doubling and Halving strategy?
Double one number and halve the other to make multiplication easier, especially with 5 and 25.
How do you use Nearest Multiple strategy?
Round one number to the nearest 10 or 100, multiply, then add or subtract the difference.
Solve: 4 × 19 using Nearest Multiple
4 × 20 = 80, then subtract 4 × 1 = 4, so 80 − 4 = 76.
What is 18 × 5 using Halving and Doubling?
Half of 18 is 9, and 9 × 10 = 90, so 18 × 5 = 90.
Multiply: 30 × 20
3 × 2 = 6, then add two zeros = 600.
What is the product when you multiply any number by 1,000?
Add three zeros to the right of the number, making it 1,000 times larger.
Solve using breaking into parts: 14 × 21
14 × 20 = 280, then 14 × 1 = 14, so 280 + 14 = 294.
What is 9 × 100? [1 mark]
When multiplying by 100, add two zeros to the right of the number.
Fill in the blank: 15 × 6 = 6 × ___ [1 mark]
Use the Commutative Property where the order of numbers doesn't change the product.
Solve 22 × 5 using the Doubling and Halving strategy. Show your steps. [2 marks]
Half of 22 is 11. Then multiply 11 by 10 to get your answer.
A family produces 35 kg of kitchen waste in 1 month. How much waste will they produce in 12 months? Use any multiplication strategy and show your working. [3 marks]
You need to find 12 × 35. You can use Nearest Multiple (12 × 40 − 12 × 5) or breaking into parts (12 × 30 + 12 × 5).
True or False: 28 × 25 can be solved easily using the Doubling and Halving strategy. Explain why or why not with an example. [2 marks]
The Doubling and Halving strategy works best with numbers like 5 and 25. Half of 28 is 14, and 14 × 50 = 700.
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