Mental addition and subtraction (age 9+) · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Adding and subtracting big numbers in your head

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

  1. What is 2,500 + 2,600?

    • 4,100
    • 6,100
    • 5,100
    • 5,000

  2. What is 45,000 + 8,000 mentally?

    • 48,000
    • 53,000
    • 52,000
    • 43,000

  3. What is 45,000 + 8,000?

    • 52,000
    • 53,000
    • 54,000

  4. Counting up from the smaller number is one way to subtract in your head.

    Circle one:   True   False

  5. Ava doubled 2,500 to get 5,000, then added 100 to reach 2,500 + 2,600. Is her method right?

    Circle one:   True   False

  6. Use a near-double to solve 3,400 + 3,500.

    • 6,900
    • 6,800
    • 7,000

  7. Count up from 3,200 to 10,000. How far is it?

    • 7,800
    • 6,200
    • 13,200
    • 6,800

  8. What is 10,000 - 3,200?

    Answer: ______________

  9. Omar says 4,700 − 1,300 = 3,300. Is he right?

    • Yes, 3,300 is right
    • No, the answer is 3,400
    • No, the answer is 3,500

  10. Jay says 45,000 + 8,000 = 53,000 because 45 + 8 = 53. Is Jay right?

    Circle one:   True   False

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Answer key

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

Adding and subtracting big numbers in your head W1-mt_MWXPiaTnEu-s1

  1. 5,100 · 5,100 is right: double 2,500 to get 5,000, then add the extra 100.
  2. 53,000 · 53,000 is right because 45 + 8 = 53 thousands.
  3. 53,000 · 45 thousand + 8 thousand = 53 thousand, so the answer is 53,000.
  4. True · Counting up from the smaller number to the bigger one tells you the gap between them, which is the answer.
  5. True · Ava is right: 2,600 is 100 past the double, so 5,000 + 100 = 5,100.
  6. 6,900 · 3,400 + 3,400 = 6,800, and 3,500 is 100 more than 3,400, so add that 100: 6,800 + 100 = 6,900.
  7. 6,800 · 6,800 is right because 3,200 + 6,800 = 10,000.
  8. 6800 · 10,000 - 3,200 = 6,800.
  9. No, the answer is 3,400 · Subtract the thousands and hundreds separately: 4,000 − 1,000 = 3,000 and 700 − 300 = 400, so the answer is 3,400.
  10. True · Jay is right: thousands add like ones, giving 53 thousands.
Worksheet · LightMySky