Ways to Multiply and Divide — Class 5 Mathematics (CBSE)
Based on the NCERT Math Magic Grade 5 textbook. Master multiplication and division skills, then solve the practice set without looking at the answers.
1. Why this chapter matters
Multiplication and division are the most used operations in daily life — calculating bills, sharing items equally, planning budgets, and measuring quantities. This chapter goes beyond basic tables to teach students efficient algorithms for multiplying and dividing larger numbers. Students also learn mental math strategies, estimation, and real-world problem solving. Speed and accuracy with these operations are essential for success in higher mathematics.
2. Multiplication of large numbers
Multiplication by a 1-digit number
Example 1: 3,456 x 7
3,456
x 7
-------
24,192
Working: 7 x 6 = 42 (write 2, carry 4) 7 x 5 = 35 + 4 = 39 (write 9, carry 3) 7 x 4 = 28 + 3 = 31 (write 1, carry 3) 7 x 3 = 21 + 3 = 24 (write 24)
Multiplication by a 2-digit number
Example 2: 1,234 x 23
Method: Multiply by 3 (ones digit), then by 20 (tens digit), then add.
1,234
x 23
---------
3,702 (1,234 x 3)
+ 24,680 (1,234 x 20)
---------
28,382
Lattice multiplication (alternative method)
- Draw a grid with the number of rows = digits of first number, columns = digits of second number.
- Split each cell diagonally.
- Multiply the digit at the top of each column by the digit at the left of each row.
- Write the product in the cell (tens above diagonal, ones below).
- Add diagonally, carrying when needed.
Example: 45 x 37
4 5
+---+---+
3 |1 /|1 /|
| / | / |
|/ 2|/ 5|
+---+---+
7 |2 /|3 /|
| / | / |
|/ 8|/ 5|
+---+---+
Adding diagonally from bottom-right: 5, then 5+3+8=16 (carry 1), then 1+1+2+1=5... = 1,665
3. Division of large numbers
Division by a 1-digit number
Example: 6,432 / 8
804
------
8 | 6,432
- 6,400 (8 x 800)
------
32
- 32 (8 x 4)
----
0
Answer: 804
Division by a 2-digit number
Example: 3,456 / 12
288
------
12 | 3,456
- 2,400 (12 x 200)
------
1,056
- 960 (12 x 80)
------
96
- 96 (12 x 8)
----
0
Answer: 288
Checking division
Dividend = Divisor x Quotient + Remainder
For the above: 12 x 288 + 0 = 3,456. Correct.
4. Word problems
Problem 1: A factory produces 2,450 notebooks each day. How many notebooks does it produce in 25 days? 2,450 x 25 = 2,450 x 20 + 2,450 x 5 = 49,000 + 12,250 = 61,250 notebooks.
Problem 2: 5,760 pencils are packed equally into 24 boxes. How many pencils in each box? 5,760 / 24 = 240 pencils per box.
Problem 3: A train travels 1,250 km in 5 hours. What is its speed per hour? 1,250 / 5 = 250 km per hour.
Problem 4: A book costs Rs 185. What is the cost of 36 such books? 185 x 36 = 185 x 30 + 185 x 6 = 5,550 + 1,110 = Rs 6,660.
5. Mental math strategies
Multiplication tricks
| Strategy | Example | Working |
|---|---|---|
| Multiply by 10 | 45 x 10 | Add a zero: 450 |
| Multiply by 100 | 45 x 100 | Add two zeros: 4,500 |
| Multiply by 5 | 46 x 5 | Half and then x10: 46/2=23, 23x10=230 |
| Multiply by 25 | 48 x 25 | Quarter and then x100: 48/4=12, 12x100=1,200 |
| Multiply by 9 | 36 x 9 | (36 x 10) — 36 = 360 — 36 = 324 |
| Multiply by 11 | 42 x 11 | 4(4+2)2 = 462 |
Division tricks
| Strategy | Example | Working |
|---|---|---|
| Divide by 10 | 450 / 10 | Remove a zero: 45 |
| Divide by 100 | 4,500 / 100 | Remove two zeros: 45 |
| Divide by 5 | 240 / 5 | Double then /10: 240x2=480, 480/10=48 |
| Divide by 25 | 600 / 25 | Times 4 then /100: 600x4=2,400, 2,400/100=24 |
6. Estimation
Before calculating exactly, estimate to check if the answer is reasonable.
Example: Estimate 4,890 x 32.
Round 4,890 to 5,000. Round 32 to 30. Estimated product = 5,000 x 30 = 1,50,000. The actual answer should be close to 1,50,000.
Example: Estimate 5,720 / 28.
Round 5,720 to 6,000. Round 28 to 30. Estimated quotient = 6,000 / 30 = 200. Actual answer: 5,720 / 28 = 204.2... Close to 200.
7. Activity corner
Activity 1: Find the total number of pages in 12 notebooks if each notebook has 168 pages. Estimate first, then calculate exactly.
Activity 2: A school has 960 students. They are divided into 24 equal sections. How many students in each section? Check by multiplying.
Activity 3: Practice mental math with a partner. Take turns giving each other problems like 50 x 30, 120 x 5, 400 / 20, 3,600 / 12. Time each other.
8. Common mistakes
- Mistake: Forgetting to carry in multiplication Fix: Write the carry digit clearly above the next column. Double-check each step.
- Mistake: Misaligning digits in the partial products Fix: When multiplying by the tens digit, start writing the result below the tens place.
- Mistake: Forgetting to bring down digits in long division Fix: Bring down one digit at a time. If the divisor cannot divide, write 0 in the quotient and bring down the next digit.
- Mistake: Not checking the answer Fix: Always check: Product ÷ Multiplier = Multiplicand. Or: Divisor x Quotient + Remainder = Dividend.
9. Key facts
- Multiply large numbers step by step, starting from the ones digit.
- In division, remember: Dividend = Divisor x Quotient + Remainder.
- Estimate before calculating to check if the answer is reasonable.
- Use mental math tricks for quick calculations with 5, 9, 10, 11, 25, etc.
- Always align digits correctly in the ones, tens, hundreds columns.
- Check your answers by performing the reverse operation.
10. Self-test
- Multiply: 2,345 x 6.
- Multiply: 1,256 x 34.
- Divide: 4,896 / 8.
- Divide: 7,200 / 24.
- Estimate: 6,120 x 48. Round to the nearest thousand and ten.
11. Answer key
-
Multiply: 2,345 x 6. Answer: 2,345 x 6 = 14,070.
-
Multiply: 1,256 x 34. Answer: 1,256 x 34 = 1,256 x 30 + 1,256 x 4 = 37,680 + 5,024 = 42,704.
-
Divide: 4,896 / 8. Answer: 4,896 / 8 = 612. Check: 612 x 8 = 4,896.
-
Divide: 7,200 / 24. Answer: 7,200 / 24 = 300. Check: 300 x 24 = 7,200.
-
Estimate: 6,120 x 48. Answer: Round 6,120 to 6,000. Round 48 to 50. Estimate = 6,000 x 50 = 3,00,000. Actual = 6,120 x 48 = 2,93,760. The estimate is close.
12. Quick revision
- Multiply: align digits, multiply each place, add partial products.
- Divide: find how many times the divisor fits into the dividend.
- Estimate first, calculate exactly, then check.
- Use mental math tricks for speed.
- Practise word problems by reading carefully and identifying the operation.
- Always check: reverse operation verifies your answer.
