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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 572 · 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. 1.20 + 29 =
  2. 2.17 + 29 =
  3. 3.446 + 99 =
  4. 4.507 + 99 =
  5. 5.84 − 19 =
  6. 6.659 + 99 =
  7. 7.668 + 99 =
  8. 8.297 − 99 =
  9. 9.72 + 19 =
  10. 10.71 + 19 =
  11. 11.47 + 29 =
  12. 12.395 + 99 =
  13. 13.36 + 29 =
  14. 14.52 − 9 =
  15. 15.503 − 99 =
  16. 16.676 + 99 =
  17. 17.70 − 9 =
  18. 18.62 + 9 =
  19. 19.54 + 29 =
  20. 20.66 − 9 =
  21. 21.21 + 19 =
  22. 22.546 + 99 =
  23. 23.33 − 29 =
  24. 24.48 + 19 =
  25. 25.87 − 29 =
  26. 26.229 + 99 =
  27. 27.68 + 9 =
  28. 28.44 − 19 =
  29. 29.48 + 29 =
  30. 30.315 − 99 =
  31. 31.51 − 29 =
  32. 32.38 − 9 =
  33. 33.17 − 9 =
  34. 34.484 + 99 =
  35. 35.26 + 19 =
  36. 36.32 − 19 =
  37. 37.58 − 9 =
  38. 38.77 − 19 =
  39. 39.34 + 9 =
  40. 40.222 + 99 =

Answer key

  1. 49
  2. 46
  3. 545
  4. 606
  5. 65
  6. 758
  7. 767
  8. 198
  9. 91
  10. 90
  11. 76
  12. 494
  13. 65
  14. 43
  15. 404
  16. 775
  17. 61
  18. 71
  19. 83
  20. 57
  21. 40
  22. 645
  23. 4
  24. 67
  25. 58
  26. 328
  27. 77
  28. 25
  29. 77
  30. 216
  31. 22
  32. 29
  33. 8
  34. 583
  35. 45
  36. 13
  37. 49
  38. 58
  39. 43
  40. 321

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