📘 What's inside:
Concept 1 — Multiplying a 2-Digit Number by a 1-Digit Number
```To multiply a 2-digit number by a single digit, we use the column method. We multiply the 1-digit number with the Ones digit first, carry if needed, then multiply with the Tens digit and add any carry.
- Write the 2-digit number on top. Write the 1-digit number below it, aligned to the right.
- Write the × sign to the left. Draw a line.
- Step 1: Multiply the 1-digit number by the Ones digit. If the result ≥ 10, write the units digit below and carry the tens digit.
- Step 2: Multiply the 1-digit number by the Tens digit. Add any carry. Write the result.
- Draw a double line. Read the answer.
- 1Ones: 6 × 7 = 42. Write 2, carry 4.
- 2Tens: 6 × 4 = 24, + 4 (carry) = 28. Write 28.
✍ Practice — Concept 1
Concept 2 — Multiplying a 3-Digit Number by a 1-Digit Number
```Same method — but now we have three steps: multiply the 1-digit number by Ones, then Tens, then Hundreds, carrying each time if needed.
- 1O: 6×8=48 → write 8, carry 4.
- 2T: 6×4=24, +4=28 → write 8, carry 2.
- 3H: 6×3=18, +2=20. Write 20.
✍ Practice — Concept 2
Concept 3 — Multiplying a 2-Digit Number by a 2-Digit Number
```When the multiplier has two digits, we multiply twice — once by the Ones digit and once by the Tens digit — giving two partial products. The second partial product is shifted one place to the left (or a × placeholder is written). Then we add both partial products to get the final answer.
- Write the larger number on top, the multiplier below it. Draw a line.
- Step 1 (Ones): Multiply the top number by the Ones digit of the multiplier. Write this as the 1st partial product (PP1) — no shift.
- Step 2 (Tens): Multiply the top number by the Tens digit of the multiplier. Write this as the 2nd partial product (PP2) — shifted one place left (write × in the Ones place as a placeholder).
- Draw a second line. Add PP1 and PP2. This is the final product.
The 2nd partial product (from the Tens digit) is always shifted one place to the left. Write a × symbol (or 0) in the Ones column of PP2 as a placeholder. Forgetting this shift is the most common mistake in long multiplication.
- 1Multiply 23 × 2 (ones digit of 12) = 46. Write as PP1.
- 2Multiply 23 × 1 (tens digit of 12) = 23. Write as PP2 with × placeholder (shifted left). PP2 = 23× = 230.
- 3Add: 46 + 230 = 276.
- 1PP1: 47 × 5 = 235. (7×5=35, write 5 carry 3; 4×5=20+3=23)
- 2PP2: 47 × 3 = 141. Write 141× (shifted one left = 1410).
- 3Add: 235 + 1410 = 1645.
✍ Practice — Concept 3
Correct: PP1 = 45×3 = 135. PP2 = 45×2 = 90× = 900. Total = 135 + 900 = 1035.
Concept 4 — Multiplying a 3-Digit Number by a 2-Digit Number
```Exactly the same method — two partial products, same shift rule. Now the partial products are larger since we are multiplying a 3-digit number each time.
- 1PP1: 124 × 2 = 248. (4×2=8, 2×2=4, 1×2=2)
- 2PP2: 124 × 3 = 372. Write 372× (= 3720).
- 3Add: 248 + 3720 = 3968.
- 1PP1: 356 × 7:
6×7=42 → write 2, carry 4.
5×7=35, +4=39 → write 9, carry 3.
3×7=21, +3=24 → write 24.
PP1 = 2492. - 2PP2: 356 × 4:
6×4=24 → write 4, carry 2.
5×4=20, +2=22 → write 2, carry 2.
3×4=12, +2=14 → write 14.
PP2 = 1424× = 14240. - 3Add: 2492 + 14240 = 16,732.
✍ Practice — Concept 4
PP2: 245×3 = 735× = 7350 (not 735!)
Correct addition: 1470 + 7350 = 8820.
Mistake: The student added 1470 + 735 instead of 1470 + 7350. They forgot that PP2× = PP2 shifted left = PP2 × 10.
Concept 5 — Word Problems
```For word problems involving multiplication, look for key words like each, every, per, total, altogether, times, groups of. Identify the two factors and multiply using the long multiplication method.
- 1Books per box = 48. Number of boxes = 35. Find 48 × 35.
✍ Practice — Concept 5
The train has 1,152 seats in total.
The farmer plants 15,300 trees altogether.
The shop sells 14,300 packets in 52 weeks.
- Always multiply Ones first, then Tens, then Hundreds. Carry where needed.
- When multiplying by a 2-digit multiplier, write two partial products: PP1 (ones digit × top) and PP2 (tens digit × top).
- PP2 is always shifted one place left — write a × placeholder in the Ones column of PP2.
- The × placeholder means PP2 is worth 10 times its face value.
- After writing both partial products, add them to get the final answer.
- Always verify: a rough estimate (round both numbers) should be close to your answer.
Exam Style — Class 3, 4 & 5
5 Questions on Multiplying 2–3 Digit Numbers
PP1 = 328×5 = 1640 PP2 = 328×4 = 1312 Answer = 1640 + 1312 = 2952.
Find the correct answer. What was the mistake? ▼
Mistake: The student added PP2 as 1312 instead of 13120. They forgot the × shift (forgot to multiply PP2 by 10).
13,680 tickets were sold in total.
Exact working:
Estimate was 32,900 — close to 34,237. ✓
Practise 2–3 digit multiplication with full long multiplication layout, partial products, carries and word problems. No login required.
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