Rounding and estimating
Round to the nearest 10, 100 or 1 000, and estimate an answer before you calculate. Read one step, play with it, then tap “I understand this”.
What does rounding mean?
Rounding gives a number that is close and easy to work with. 47 is close to 50, so 47 rounded to the nearest 10 is 50. We write 47 ≈ 50.
The rounding line
Change the number. The green arrow jumps to the nearest round number.
Look at the digit to its right
You do not have to draw a number line every time. Look at just one digit: the digit to the right of the place you round to.
- Nearest 10: look at the ones.
- Nearest 100: look at the tens.
- Nearest 1 000: look at the hundreds.
0, 1, 2, 3, 4: round down. 5, 6, 7, 8, 9: round up.
4 682 ≈ 4 680 · 4 700 · 5 000
45 is exactly halfway between 40 and 50. Both are equally far, so mathematicians agreed that the middle always goes up. Then everyone gets the same answer.
Practise rounding
Round it
Choose what to round to, then pick the right answer.
Correct: 0Estimate before you calculate
Estimating is a clever guess. Round the numbers, calculate with the round numbers, and you know roughly how big the answer should be.
The estimating machine
Estimate yourself first, then tap “Show the estimate”.
Is your exact answer far from the estimate? Work through the sum again: there is probably a mistake.
An estimate is your safety net. If your answer is far from the estimate, you know straight away there is a mistake, before you hand it in.
Traps
Exactly halfway always rounds up: 45 ≈ 50, 350 ≈ 400, 2 500 ≈ 3 000.
395 to the nearest 10 is 400, not 390 or 3 100. The 9 tens + 1 make a new hundred.
Rounding does not change the size: 4 682 to the nearest 100 is 4 700, not 47. The places after rounding become 0.
Check yourself
- Look at the digit to the right of the place you round to.
- 0 to 4: round down. 5 to 9: round up.
- The places after rounding become 0: 4 682 ≈ 4 700.
- Estimate before you calculate, and compare your answer with the estimate.
Write these points in your maths book. Read them again the night before the test.
Quick questions
Tap an answer. If you get one wrong, read why and go back to that step. You get new questions every time.
You ticked all 5 steps! Now you are ready for the quiz.- Practice sheet for this classQuestions + memo · 2 A4 pagesPractice sheet
- Numbers14 pages · PDFPaperMemo
Ready for more? The Grade 4 rounding quiz gives you new numbers every time.
- One step a day is enough. Ten calm minutes work better than an hour the night before the test.
- Estimate together at the shop: “We buy something for R38 and something for R53. Is R100 enough?” That is rounding in real life.
- Ask your child to tell you the rule in their own words. If they can explain it, they understand it.
- The ticks (“I understand this”) are saved on this device only. We never ask for names or emails.
Follows CAPS for Grade 4 Maths. Always check your teacher’s notes and textbook too.