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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 323 · 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. 1.56 + 9 =
  2. 2.734 − 99 =
  3. 3.51 + 19 =
  4. 4.60 − 19 =
  5. 5.517 − 99 =
  6. 6.50 + 19 =
  7. 7.20 + 9 =
  8. 8.89 − 9 =
  9. 9.454 − 99 =
  10. 10.67 − 29 =
  11. 11.364 + 99 =
  12. 12.430 − 99 =
  13. 13.21 + 9 =
  14. 14.522 − 99 =
  15. 15.77 + 19 =
  16. 16.36 − 19 =
  17. 17.282 + 99 =
  18. 18.269 − 99 =
  19. 19.13 − 9 =
  20. 20.412 + 99 =
  21. 21.77 − 19 =
  22. 22.50 + 9 =
  23. 23.88 − 9 =
  24. 24.26 + 9 =
  25. 25.798 + 99 =
  26. 26.370 − 99 =
  27. 27.73 + 19 =
  28. 28.746 + 99 =
  29. 29.195 − 99 =
  30. 30.76 + 29 =
  31. 31.68 + 9 =
  32. 32.42 − 19 =
  33. 33.107 − 29 =
  34. 34.631 + 99 =
  35. 35.46 − 9 =
  36. 36.630 − 99 =
  37. 37.52 + 19 =
  38. 38.338 − 99 =
  39. 39.40 + 9 =
  40. 40.69 + 29 =

Answer key

  1. 65
  2. 635
  3. 70
  4. 41
  5. 418
  6. 69
  7. 29
  8. 80
  9. 355
  10. 38
  11. 463
  12. 331
  13. 30
  14. 423
  15. 96
  16. 17
  17. 381
  18. 170
  19. 4
  20. 511
  21. 58
  22. 59
  23. 79
  24. 35
  25. 897
  26. 271
  27. 92
  28. 845
  29. 96
  30. 105
  31. 77
  32. 23
  33. 78
  34. 730
  35. 37
  36. 531
  37. 71
  38. 239
  39. 49
  40. 98

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