Three game modes
- Where is it? – the game gives you a number and you show where it is on the number line. Tap, or drag the marker into place. The closer you are, the more points you get (10 numbers a round, up to 10 points each).
- Which number? – an arrow points at a tick on the line; count the divisions to work out which number it marks.
- Rounding – round to the nearest ten, hundred or thousand. After each answer a small number line shows which round number it is closer to.
Choose the length of the line: 0–100, 0–1,000 or 0–10,000. As on school worksheets, only 0, the middle and the end are labelled – everything else you work out from the ticks.
Rounding step by step
- Find the place you are rounding to. The tens place when rounding to the nearest ten, the hundreds place for the nearest hundred.
- Look at the digit just to its right. This is the deciding digit.
- 0–4: round down, 5–9: round up. Rounding down keeps the digit in the rounding place; rounding up adds one to it. Every digit after it becomes 0.
| Number | Nearest 10 | Nearest 100 | Nearest 1,000 |
|---|---|---|---|
| 4,372 | 4,370 | 4,400 | 4,000 |
| 6,845 | 6,850 | 6,800 | 7,000 |
| 2,509 | 2,510 | 2,500 | 3,000 |
| 9,951 | 9,950 | 10,000 | 10,000 |
Note: 6,845 rounded to the nearest hundred is 6,800 – the 4 in the tens place decides; the 5 in the ones place no longer matters.
Number line tips
- Find the middle first. Between 0 and 10,000 the middle is 5,000 – so you know straight away which half to look in.
- Then the big divisions. Split into ten equal parts, each part is 1,000 (100 on a 0–1,000 line, 10 on a 0–100 line).
- Finally estimate within the section. 4,350 is between 4,000 and 5,000, a little before the halfway point.
Frequently asked questions
What is the rule for rounding?
Look at the digit just to the right of the place you are rounding to (the deciding digit). If it is 0, 1, 2, 3 or 4, round down; if it is 5, 6, 7, 8 or 9, round up. To the nearest ten: 43 ≈ 40, 45 ≈ 50, 47 ≈ 50.
How do you round to the nearest hundred?
The tens digit decides. 3,249 ≈ 3,200 because there is a 4 in the tens place; 3,251 ≈ 3,300 because there is a 5. The ones digit does not matter any more.
Do you round 5 up or down?
Up, by the usual school rule: 35 ≈ 40, 250 ≈ 300, 4,500 ≈ 5,000. The number is exactly halfway, so a convention is needed – and this is it.
How can I place a number accurately on a number line?
Find the big divisions first: between 0 and 10,000 each big division is 1,000 and the middle is 5,000. So 4,350 is in the section between 4,000 and 5,000, a little before its middle. Estimate step by step like this.
How does the "Where is it?" mode score?
If your marker is within 1% of the length of the line you get 10 points; further away you get fewer, and nothing beyond 10% of the length. Your grade at the end of the round comes from the total.
More practice: Metric conversion · Roman numerals · Compass directions