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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 310 · 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. 1.98 − 29 =
  2. 2.172 + 99 =
  3. 3.14 + 29 =
  4. 4.18 − 9 =
  5. 5.288 + 99 =
  6. 6.31 + 9 =
  7. 7.411 + 99 =
  8. 8.15 + 19 =
  9. 9.62 + 29 =
  10. 10.25 + 9 =
  11. 11.74 + 29 =
  12. 12.103 − 29 =
  13. 13.16 + 19 =
  14. 14.356 − 99 =
  15. 15.55 − 29 =
  16. 16.591 − 99 =
  17. 17.23 − 19 =
  18. 18.23 − 9 =
  19. 19.77 − 9 =
  20. 20.57 + 29 =
  21. 21.30 + 19 =
  22. 22.351 − 99 =
  23. 23.43 + 9 =
  24. 24.786 + 99 =
  25. 25.58 − 9 =
  26. 26.15 + 9 =
  27. 27.740 − 99 =
  28. 28.31 + 19 =
  29. 29.296 + 99 =
  30. 30.32 + 19 =
  31. 31.86 − 9 =
  32. 32.640 + 99 =
  33. 33.42 + 19 =
  34. 34.71 − 29 =
  35. 35.76 + 29 =
  36. 36.76 + 9 =
  37. 37.271 + 99 =
  38. 38.37 − 29 =
  39. 39.97 − 19 =
  40. 40.70 + 29 =

Answer key

  1. 69
  2. 271
  3. 43
  4. 9
  5. 387
  6. 40
  7. 510
  8. 34
  9. 91
  10. 34
  11. 103
  12. 74
  13. 35
  14. 257
  15. 26
  16. 492
  17. 4
  18. 14
  19. 68
  20. 86
  21. 49
  22. 252
  23. 52
  24. 885
  25. 49
  26. 24
  27. 641
  28. 50
  29. 395
  30. 51
  31. 77
  32. 739
  33. 61
  34. 42
  35. 105
  36. 85
  37. 370
  38. 8
  39. 78
  40. 99

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