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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 631 · 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. 1.63 + 9 =
  2. 2.88 − 29 =
  3. 3.290 + 99 =
  4. 4.236 − 99 =
  5. 5.55 + 9 =
  6. 6.65 + 19 =
  7. 7.48 + 19 =
  8. 8.27 + 19 =
  9. 9.69 + 9 =
  10. 10.800 − 99 =
  11. 11.54 + 19 =
  12. 12.31 − 19 =
  13. 13.122 + 99 =
  14. 14.234 + 99 =
  15. 15.54 + 29 =
  16. 16.57 + 19 =
  17. 17.40 − 29 =
  18. 18.47 − 19 =
  19. 19.29 + 29 =
  20. 20.50 − 9 =
  21. 21.60 − 29 =
  22. 22.47 + 29 =
  23. 23.78 + 29 =
  24. 24.31 + 29 =
  25. 25.465 + 99 =
  26. 26.22 + 9 =
  27. 27.32 + 9 =
  28. 28.224 + 99 =
  29. 29.63 + 19 =
  30. 30.21 − 9 =
  31. 31.45 − 29 =
  32. 32.665 + 99 =
  33. 33.233 + 99 =
  34. 34.415 + 99 =
  35. 35.22 − 9 =
  36. 36.56 − 19 =
  37. 37.309 + 99 =
  38. 38.57 − 9 =
  39. 39.80 + 29 =
  40. 40.66 − 29 =

Answer key

  1. 72
  2. 59
  3. 389
  4. 137
  5. 64
  6. 84
  7. 67
  8. 46
  9. 78
  10. 701
  11. 73
  12. 12
  13. 221
  14. 333
  15. 83
  16. 76
  17. 11
  18. 28
  19. 58
  20. 41
  21. 31
  22. 76
  23. 107
  24. 60
  25. 564
  26. 31
  27. 41
  28. 323
  29. 82
  30. 12
  31. 16
  32. 764
  33. 332
  34. 514
  35. 13
  36. 37
  37. 408
  38. 48
  39. 109
  40. 37

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