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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 492 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.16 + 9 =
  2. 2.69 − 9 =
  3. 3.17 + 9 =
  4. 4.71 − 29 =
  5. 5.61 + 29 =
  6. 6.88 − 29 =
  7. 7.287 + 99 =
  8. 8.356 + 99 =
  9. 9.53 − 19 =
  10. 10.70 + 9 =
  11. 11.614 − 99 =
  12. 12.216 − 99 =
  13. 13.406 − 99 =
  14. 14.19 + 9 =
  15. 15.30 + 19 =
  16. 16.481 − 99 =
  17. 17.50 − 29 =
  18. 18.68 + 9 =
  19. 19.36 − 29 =
  20. 20.58 + 9 =
  21. 21.13 + 9 =
  22. 22.90 − 19 =
  23. 23.588 + 99 =
  24. 24.415 + 99 =
  25. 25.36 + 9 =
  26. 26.34 + 19 =
  27. 27.67 − 29 =
  28. 28.37 + 9 =
  29. 29.53 + 29 =
  30. 30.51 − 29 =
  31. 31.239 + 99 =
  32. 32.571 + 99 =
  33. 33.496 − 99 =
  34. 34.72 − 9 =
  35. 35.65 − 19 =
  36. 36.77 − 9 =
  37. 37.38 − 29 =
  38. 38.60 + 29 =
  39. 39.64 + 9 =
  40. 40.27 + 9 =

Answer key

  1. 25
  2. 60
  3. 26
  4. 42
  5. 90
  6. 59
  7. 386
  8. 455
  9. 34
  10. 79
  11. 515
  12. 117
  13. 307
  14. 28
  15. 49
  16. 382
  17. 21
  18. 77
  19. 7
  20. 67
  21. 22
  22. 71
  23. 687
  24. 514
  25. 45
  26. 53
  27. 38
  28. 46
  29. 82
  30. 22
  31. 338
  32. 670
  33. 397
  34. 63
  35. 46
  36. 68
  37. 9
  38. 89
  39. 73
  40. 36

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