Multiplication of Numbers III – Basic 3 Mathematics Lesson Note (Second Term)

A. counting skill: numbers 791-810

Counting from 791 to 810: 791, 792, 793, 794, 795, 796, 797, 798, 799, 800, 801, 802, 803, 804, 805, 806, 807, 808, 809, 810

Practice counting:

• From 795 to 805: _______
• From 802 to 810: _______
• Backwards from 810 to 800: _______

Skip counting by 5s: 790, 795, 800, 805, 810

Fill in missing numbers:

• 796, 797, _____, 799, _____
• 805, _____, 807, _____, 809
• _____, 792, _____, 794, _____

Special number – 800: 800 = Eight hundred (a new hundred!)

B. writing skill: writing of the numbers

Write in words:

• 791 = Seven hundred and ninety-one
• 795 = Seven hundred and ninety-five
• 800 = Eight hundred
• 805 = Eight hundred and five
• 810 = Eight hundred and ten

Write in figures:

• Seven hundred and ninety-three = _______
• Seven hundred and ninety-eight = _______
• Eight hundred and two = _______
• Eight hundred and seven = _______
• Eight hundred and nine = _______

Practice:

• 794 = _______
• 801 = _______
• Seven hundred and ninety-six = _______
• Eight hundred and four = _______

C. multiplication of three 1-digit numbers taking two at a time

What does this mean? When we have three numbers like 2 × 3 × 4, we multiply any two first, then multiply by the third.

Method 1: Multiply first two, then the third Example: 2 × 3 × 4

• Step 1: 2 × 3 = 6
• Step 2: 6 × 4 = 24
• Answer: 24

Method 2: Multiply last two, then the first Example: 2 × 3 × 4

• Step 1: 3 × 4 = 12
• Step 2: 2 × 12 = 24
• Answer: 24 (same result!)

More examples:

1. 3 × 2 × 5:
   1. Method 1: 3 × 2 = 6, then 6 × 5 = 30
   2. Method 2: 2 × 5 = 10, then 3 × 10 = 30
2. 4 × 2 × 3:
   1. Method 1: 4 × 2 = 8, then 8 × 3 = 24
   2. Method 2: 2 × 3 = 6, then 4 × 6 = 24

Practice multiplication:

1. 2 × 3 × 2 = _____
2. 3 × 2 × 4 = _____
3. 2 × 4 × 2 = _____
4. 3 × 3 × 2 = _____
5. 2 × 2 × 5 = _____
6. 4 × 2 × 2 = _____
7. 3 × 2 × 3 = _____
8. 2 × 5 × 2 = _____

Step by step practice: Example: 2 × 4 × 3

• First multiply: 2 × 4 = _____
• Then multiply: _____ × 3 = _____

Try these:

1. 3 × 2 × 5:
   1. First: 3 × 2 = _____
   2. Then: _____ × 5 = _____
2. 4 × 2 × 2:
   1. First: 4 × 2 = _____
   2. Then: _____ × 2 = _____

D. quantitative reasoning

Word problems:

1. There are 3 boxes. Each box has 2 packets. Each packet has 4 sweets. How many sweets are there altogether?
2. A garden has 2 rows. Each row has 3 plants. Each plant has 5 flowers. How many flowers are there in total?
3. Kemi buys 4 bags. Each bag has 2 oranges. She buys 3 such sets. How many oranges does she have?

Pattern completion:

1. 2 × 2 × 2 = 8, 2 × 2 × 3 = _____, 2 × 2 × 4 = _____
2. 3 × 2 × 1 = 6, 3 × 2 × 2 = _____, 3 × 2 × 3 = _____

Choose the easier way: Which way is easier to multiply?

1. 2 × 5 × 3: (2 × 5) × 3 or 2 × (5 × 3)? _____
2. 4 × 2 × 5: (4 × 2) × 5 or 4 × (2 × 5)? _____

Missing numbers:

1. 2 × _____ × 3 = 18
2. _____ × 2 × 4 = 24
3. 3 × 3 × _____ = 27

CLASS EXERCISES

1. Count from 798 to 808:
2. Write in words:
   1. 797 = _______
   2. 800 = _______
   3. 806 = _______
3. Write in figures:
   1. Seven hundred and ninety-nine = _______
   2. Eight hundred and three = _______
4. Multiply three numbers:
   1. 2 × 3 × 3 = _____
   2. 2 × 4 × 2 = _____
   3. 3 × 2 × 4 = _____
   4. 2 × 2 × 5 = _____
5. Show your steps:
   1. 3 × 2 × 3: First: _____ × _____ = _____ Then: _____ × _____ = _____
6. Word problems:
   1. There are 2 shelves. Each shelf has 3 boxes. Each box has 4 books. How many books are there?
   2. A farmer has 3 fields. Each field has 2 rows. Each row has 5 plants. How many plants in total?
7. Complete the patterns:
   1. 2 × 3 × 2 = 12, 2 × 3 × 3 = _____, 2 × 3 × 4 = _____
8. Find the missing numbers:
   1. 2 × _____ × 4 = 16
   2. _____ × 3 × 2 = 18
9. Choose the easier method and solve:
   1. 2 × 5 × 4 = _____
   2. 3 × 2 × 5 = _____
10. Problem solving: A baker makes 3 trays of cookies. Each tray has 4 rows. Each row has 2 cookies. How many cookies did he make?