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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 541 · 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 + 9 =
  2. 2.56 + 9 =
  3. 3.401 − 99 =
  4. 4.84 − 19 =
  5. 5.376 − 99 =
  6. 6.86 − 9 =
  7. 7.68 + 9 =
  8. 8.399 + 99 =
  9. 9.76 − 19 =
  10. 10.27 + 29 =
  11. 11.243 + 99 =
  12. 12.316 + 99 =
  13. 13.52 − 29 =
  14. 14.64 + 9 =
  15. 15.88 − 9 =
  16. 16.21 + 9 =
  17. 17.380 + 99 =
  18. 18.25 + 9 =
  19. 19.76 − 9 =
  20. 20.20 − 9 =
  21. 21.43 + 29 =
  22. 22.58 − 9 =
  23. 23.70 − 29 =
  24. 24.744 + 99 =
  25. 25.28 + 29 =
  26. 26.53 + 29 =
  27. 27.448 − 99 =
  28. 28.56 − 9 =
  29. 29.58 − 19 =
  30. 30.72 + 9 =
  31. 31.69 − 29 =
  32. 32.80 − 9 =
  33. 33.59 − 9 =
  34. 34.47 + 9 =
  35. 35.751 − 99 =
  36. 36.41 − 9 =
  37. 37.59 + 19 =
  38. 38.22 + 19 =
  39. 39.20 + 19 =
  40. 40.125 + 99 =

Answer key

  1. 29
  2. 65
  3. 302
  4. 65
  5. 277
  6. 77
  7. 77
  8. 498
  9. 57
  10. 56
  11. 342
  12. 415
  13. 23
  14. 73
  15. 79
  16. 30
  17. 479
  18. 34
  19. 67
  20. 11
  21. 72
  22. 49
  23. 41
  24. 843
  25. 57
  26. 82
  27. 349
  28. 47
  29. 39
  30. 81
  31. 40
  32. 71
  33. 50
  34. 56
  35. 652
  36. 32
  37. 78
  38. 41
  39. 39
  40. 224

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