5 min read
Mathew Wahome
Whole Numbers
Place value
In the Junior School CBC (KICD), Grade 7 Mathematics starts with Numbers, building on whole numbers. Each digit has a value that depends on its position.
| Millions | Hundred thousands | Ten thousands | Thousands | Hundreds | Tens | Ones |
|---|---|---|---|---|---|---|
| 3 | 4 | 7 | 2 | 0 | 1 | 5 |
3,472,015 reads: three million, four hundred seventy-two thousand and fifteen.
Total value and place value
In 3,472,015, the place value of 7 is ten thousands; its total value is 70,000.
Rounding
Look at the digit to the right of the rounding place. If it is 5 or more, round up; otherwise keep the digit.
- 48,639 to the nearest thousand: 49,000.
- 48,639 to the nearest hundred: 48,600.
Operations
- Addition and subtraction: line up digits by place value and carry or borrow.
- Multiplication: 25 x 12 = 25 x 10 + 25 x 2 = 250 + 50 = 300.
- Division: 756 / 4 = 189.
Order of operations (BODMAS)
Brackets, Orders (powers), Division and Multiplication, Addition and Subtraction.
Worked example: 6 + 4 x 3 = 6 + 12 = 18. And (6 + 4) x 3 = 30.
Divisibility tests
- By 2: ends in an even digit.
- By 3: digit sum divisible by 3.
- By 5: ends in 0 or 5.
- By 9: digit sum divisible by 9.
- By 10: ends in 0.
Example: 5,310 has digit sum 9, so it is divisible by 3 and 9, and by 5 and 10.
Try it
- Write 5,060,203 in words.
- Round 76,482 to the nearest ten thousand.
- Work out 3 + 8 x (10 - 6) / 2.
- Is 2,718 divisible by 9? Show why.