Primary 4 Numbers up to 100 000
Read, write, compare, order and round numbers up to 100 000. Use place value to explain each digit and ≈ to show an estimate.
Keywords
- Digit
- One symbol from 0 to 9.
- Place value
- What a digit is worth because of its position.
- Expanded form
- A number written as the sum of its nonzero place values.
- Increasing order
- Smallest to largest.
- Decreasing order
- Largest to smallest.
- Rounding
- Replacing a number with the nearest multiple of 10, 100 or 1 000.
- Estimation (≈)
- An approximate value used to check or predict an answer.
Read and write numbers
A five-digit number starts with ten thousands. Read the thousands part, then the last three digits. Keep every zero in the numeral because each zero holds its place.
When do we use each mark?
A ✓ means the mark appears in that example. A hyphen can also join the two-digit thousands part, as in fifty-two thousand.
| No. | Comma | ‘and’ | Hyphen | Example | |
|---|---|---|---|---|---|
| 1 | × | × | × | 40 000 | forty thousand |
| 2 | × | ✓ | × | 40 005 | forty thousand and five |
| 3 | × | ✓ | × | 40 300 | forty thousand and three hundred |
| 4 | ✓ | ✓ | × | 40 320 | forty thousand, three hundred and twenty |
| 5 | ✓ | ✓ | ✓ | 40 325 | forty thousand, three hundred and twenty-five |
| 6 | × | × | ✓ | 52 000 | fifty-two thousand |
In numerals, separate the last three digits with a space: 40 325 and 100 000.
See worked example
Write 52 341 in words. Write “seventy thousand and eighty” in numerals.
- 52 is the thousands part: fifty-two thousand.
- 341 is three hundred and forty-one.
- In seventy thousand and eighty, the hundreds and ones places are empty, so keep their zeros.
Answer: fifty-two thousand, three hundred and forty-one; 70 080.
Try together
Write 40 005 in words. Write “ninety-six thousand, two hundred and seven” in numerals.
Reveal the answer
forty thousand and five; 96 207.
Five-digit place value
A digit tells you how many; its place tells you what each one is worth. The same digit becomes worth ten times as much each time it moves one place to the left.
Tap a digit to find its value
Tap a digit. The 5 in 52 341 is worth 50 000.
See worked example
What is the value of the 5 in 52 341? Write the number in expanded form.
- Put each digit in its place: 5 ten thousands, 2 thousands, 3 hundreds, 4 tens and 1 one.
- The 5 is in the ten-thousands place, so its value is 5 × 10 000 = 50 000.
- Add the values of the nonzero digits.
Answer: The 5 is worth 50 000; 52 341 = 50 000 + 2 000 + 300 + 40 + 1.
Try together
What is the value of the 7 in 74 706? Write the number in expanded form.
Reveal the answer
The first 7 is worth 70 000 and the second 7 is worth 700. 74 706 = 70 000 + 4 000 + 700 + 6.
Compare and order numbers
Compare from the largest place. The first place where the digits differ decides which number is greater. Increasing order goes from smallest to largest; decreasing order reverses the same sequence.
Find the first different place
| Number | Ten thousands | Thousands | Hundreds | Tens | Ones |
|---|
At the hundreds place, 3 < 4. So 52 341 < 52 431.
Ordering numbers
Order these numbers: 43 608, 43 680, 43 086
43 086 → 43 608 → 43 680
All have 43 thousands. Compare the hundreds, then the tens.
See worked example
Compare 52 341 and 52 431. Then put 43 608, 43 680 and 43 086 in increasing order.
- 52 341 and 52 431 match in the ten-thousands and thousands places.
- At the hundreds place, 3 < 4, so 52 341 < 52 431.
- The three numbers to order all have 43 thousands. Compare hundreds, then tens.
Answer: 52 341 < 52 431; increasing order: 43 086, 43 608, 43 680.
Try together
Put 90 090, 90 900 and 100 000 in decreasing order.
Reveal the answer
100 000, 90 900, 90 090. 100 000 has six digits; of the other two, 9 hundreds is greater than 0 hundreds.
Rounding numbers to the nearest 10, 100 or 1 000
Look at the digit immediately to the right of the place you are rounding to. If it is 5 or more, round up; if it is 4 or less, round down. Replace the digits to the right with zeros. Write ≈ (“approximately equal to”) when showing a rounded value or estimate.
Round 47 286
Solution steps
Start with 47 286. Show the first step.
Use ≈ for estimation
Round each number to the nearest 1 000 before adding:
47 286 + 21 409 ≈ 47 000 + 21 000 = 68 000
The exact sum is 68 695. The estimate helps check whether that answer is sensible.
See worked example
Round 47 286 to the nearest 10, 100 and 1 000. Estimate 47 286 + 21 409 by rounding both numbers to the nearest 1 000.
- Nearest 10: mark the tens digit 8, then circle the ones digit 6. Since 6 is at least 5, 47 286 ≈ 47 290.
- Nearest 100: mark the hundreds digit 2, then circle the tens digit 8. Since 8 is at least 5, 47 286 ≈ 47 300.
- Nearest 1 000: mark the thousands digit 7, then circle the hundreds digit 2. Since 2 is less than 5, 47 286 ≈ 47 000.
- Estimate the sum: 47 286 + 21 409 ≈ 47 000 + 21 000 = 68 000.
Answer: 47 290; 47 300; 47 000. The estimated sum is 68 000.
Try together
Round 63 750 to the nearest 10, 100 and 1 000. Then estimate 63 750 + 14 200 by rounding both numbers to the nearest 1 000.
Reveal the answer
63 750 ≈ 63 750 (nearest 10), 63 800 (nearest 100), and 64 000 (nearest 1 000). 63 750 + 14 200 ≈ 64 000 + 14 000 = 78 000.