Checking Answers by Rounding · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Checking your answer with rounding

Mathematics · Addition & Subtraction · ages 9-10
Name ______________________   Date ____________

  1. Estimate 23,156 + 47,832 by rounding each to the nearest thousand.

    • 71,000
    • 70,000
    • 72,000
    • 60,000

  2. Round 47,832 to the nearest thousand.

    • 47,000
    • 47,800
    • 40,000
    • 48,000

  3. What is the point of rounding numbers before checking a calculation?

    • To get a fast estimate to compare with your exact answer
    • To make the numbers bigger
    • To avoid doing the calculation at all

  4. If your exact answer is close to your rounding estimate, your exact answer is probably correct.

    Circle one:   True   False

  5. A pupil got 3,421 for a sum estimated at 50,000. She says her answer is correct. Is she right?

    Circle one:   True   False

  6. A calculation gives an answer of 3,421. Rounding the two numbers being added gives an estimate of about 50,000. What should you do?

    • Trust the exact answer, no need to check further
    • Recheck the calculation because the numbers do not match
    • Round the exact answer to 3,000

  7. Which rounding is best for checking a shop bill near £48 and £32?

    • no rounding at all
    • nearest £10
    • nearest £10,000
    • nearest million

  8. Estimate 8,947 - 3,102 by rounding to the nearest thousand.

    Answer: ______________

  9. Maya adds 62,415 + 18,290 and gets 8,705. Rounding to the nearest thousand gives an estimate of about 80,000. What does this tell Maya?

    • She should round more
    • Her answer is correct
    • Her answer is very likely wrong

  10. Mo checked 500,000 - 234,178 with 500,000 - 200,000 = 300,000 and got an exact answer near 266,000. He says his answer is sensible. Is he right?

    Circle one:   True   False

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Answer key

For grown-ups. Fold this page away before handing over the rest.

Checking your answer with rounding W1-mt_G3sVFQNCme-s1

  1. 71,000 · 71,000 is right because 23,000 + 48,000 = 71,000.
  2. 48,000 · 48,000 is right because 832 is past 500, pushing up.
  3. To get a fast estimate to compare with your exact answer · Rounding turns hard numbers into easy ones, so you can quickly estimate and compare.
  4. True · A close match is a good sign your calculation is right, like 70,988 matching an estimate of 71,000.
  5. False · She is wrong: 3,421 sits nowhere near 50,000, so the working slipped.
  6. Recheck the calculation because the numbers do not match · 3,421 is nowhere near 50,000, so the exact answer almost certainly has a mistake.
  7. nearest £10 · Nearest £10 is right: £50 + £30 = £80 checks the bill, while bigger steps erase all detail.
  8. 6000 · 9,000 - 3,000 = 6,000.
  9. Her answer is very likely wrong · 8,705 is far below the estimate of about 80,000, so something went wrong in her calculation.
  10. True · Mo is right: the exact answer 265,822 sits sensibly near 300,000.
Worksheet · LightMySky