Subtraction of Numbers Basic 3 Mathematics Lesson Note

A. COUNTING SKILLS: NUMBERS 721-750

Counting from 721 to 750: 721, 722, 723, 724, 725, 726, 727, 728, 729, 730, 731, 732, 733, 734, 735, 736, 737, 738, 739, 740, 741, 742, 743, 744, 745, 746, 747, 748, 749, 750

Practice counting:

• From 725 to 735: _______
• From 742 to 750: _______
• Backwards from 750 to 740: _______

Skip counting by 5s: 720, 725, 730, 735, 740, 745, 750

Fill in missing numbers:

• 726, 727, _____, 729, _____
• 745, _____, 747, _____, 749
• _____, 732, _____, 734, _____

B. WRITING SKILL: WRITING NUMBERS

Write in words:

• 721 = Seven hundred and twenty-one
• 725 = Seven hundred and twenty-five
• 730 = Seven hundred and thirty
• 740 = Seven hundred and forty
• 750 = Seven hundred and fifty

Write in figures:

• Seven hundred and twenty-three = _______
• Seven hundred and twenty-eight = _______
• Seven hundred and thirty-five = _______
• Seven hundred and forty-seven = _______
• Seven hundred and forty-nine = _______

Practice:

• 724 = _______
• 737 = _______
• Seven hundred and twenty-six = _______
• Seven hundred and forty-three = _______

C. SUBTRACTION WITHOUT RENAMING OR EXCHANGING

Method: Subtract units from units, tens from tens, hundreds from hundreds

Examples:

 89      567      745

– 34    – 234    – 321

—-    —–    —–

  55      333      424

Step by step for 89 – 34:

• Units: 9 – 4 = 5
• Tens: 8 – 3 = 5
• Answer: 55

Practice:

1. 78 – 25 = _____
2. 96 – 43 = _____
3. 567 – 234 = _____
4. 689 – 456 = _____
5. 745 – 312 = _____

D. SUBTRACTION WITH RENAMING OR EXCHANGING

Method: When the top digit is smaller, borrow from the next place value

Example 1: 742 – 158

  6¹³¹²

   742

 – 158

 —–

   584

Step by step:

• Units: 2 < 8, so borrow from tens: 12 – 8 = 4
• Tens: 3 < 5 (after borrowing), so borrow from hundreds: 13 – 5 = 8
• Hundreds: 6 – 1 = 5 (after borrowing)
• Answer: 584

Example 2: 63 – 28

  5¹³

   63

 – 28

 —-

   35

Practice with renaming:

1. 52 – 27 = _____
2. 81 – 36 = _____
3. 234 – 158 = _____
4. 456 – 279 = _____
5. 623 – 347 = _____

E. SUBTRACTION USING PARTIAL SUM METHOD

Breaking numbers into parts for subtraction:

Example: 567 – 234

• 567 = 500 + 60 + 7
• 234 = 200 + 30 + 4
• Hundreds: 500 – 200 = 300
• Tens: 60 – 30 = 30
• Units: 7 – 4 = 3
• Answer: 300 + 30 + 3 = 333

Practice partial sum:

1. 456 – 234:
   1. Hundreds: _____ – _____ = _____
   2. Tens: _____ – _____ = _____
   3. Units: _____ – _____ = _____
   4. Total: _____

F. QUANTITATIVE REASONING

Word problems:

1. A school had 745 pupils. 158 pupils went home sick. How many pupils remained?
2. Kemi had 623 marbles. She gave 247 to her friends. How many marbles does she have left?
3. A farmer harvested 567 oranges. He sold 289 oranges. How many oranges are left?

Number patterns:

1. 750 – 10 = 740, 740 – 10 = _____, _____ – 10 = _____
2. 500 – 100 = 400, 600 – 100 = _____, 700 – 100 = _____

Missing numbers:

1. 567 – _____ = 234
2. _____ – 189 = 345
3. 745 – 268 = _____

Estimation: Round and subtract:

1. 567 – 234 ≈ 570 – 230 = _____
2. 745 – 158 ≈ 750 – 160 = _____

CLASS EXERCISES

1. Count from 728 to 738:
2. Write in words:
   1. 727 = _______
   2. 734 = _______
   3. 750 = _______
3. Write in figures:
   1. Seven hundred and twenty-nine = _______
   2. Seven hundred and forty-six = _______
4. Subtract without renaming:
   1. 89 – 34 = _____
   2. 567 – 234 = _____
   3. 745 – 321 = _____
5. Subtract with renaming:
   1. 72 – 28 = _____
   2. 234 – 157 = _____
   3. 456 – 279 = _____
6. Use partial sum method:
   1. 567 – 234: Hundreds: _____ – _____ = _____ Tens: _____ – _____ = _____ Units: _____ – _____ = _____ Answer: _____
7. Word problems:
   1. A shop had 623 items. They sold 247 items. How many items are left?
   2. Tolu had 456 stickers. He gave away 189 stickers. How many stickers does he have now?
8. Fill in the missing numbers:
   1. 567 – _____ = 234
   2. _____ – 158 = 456
9. Estimate by rounding:
   1. 567 – 234 ≈ _____ – _____ = _____
10. Complete the pattern:
    1. 750, 740, 730, _____, _____