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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 688 · 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. 1.177 − 99 =
  2. 2.37 + 29 =
  3. 3.32 + 9 =
  4. 4.40 − 29 =
  5. 5.503 + 99 =
  6. 6.44 + 9 =
  7. 7.29 − 19 =
  8. 8.330 − 99 =
  9. 9.46 − 19 =
  10. 10.48 + 29 =
  11. 11.291 + 99 =
  12. 12.32 + 19 =
  13. 13.22 + 9 =
  14. 14.61 + 9 =
  15. 15.18 + 9 =
  16. 16.75 + 29 =
  17. 17.13 + 19 =
  18. 18.477 + 99 =
  19. 19.77 + 19 =
  20. 20.78 − 29 =
  21. 21.84 − 19 =
  22. 22.50 + 29 =
  23. 23.27 + 29 =
  24. 24.76 + 9 =
  25. 25.20 + 19 =
  26. 26.426 + 99 =
  27. 27.96 − 19 =
  28. 28.33 + 9 =
  29. 29.64 + 19 =
  30. 30.241 + 99 =
  31. 31.46 + 19 =
  32. 32.309 − 99 =
  33. 33.309 + 99 =
  34. 34.385 + 99 =
  35. 35.44 − 19 =
  36. 36.20 + 29 =
  37. 37.81 − 29 =
  38. 38.68 − 9 =
  39. 39.51 − 9 =
  40. 40.58 + 19 =

Answer key

  1. 78
  2. 66
  3. 41
  4. 11
  5. 602
  6. 53
  7. 10
  8. 231
  9. 27
  10. 77
  11. 390
  12. 51
  13. 31
  14. 70
  15. 27
  16. 104
  17. 32
  18. 576
  19. 96
  20. 49
  21. 65
  22. 79
  23. 56
  24. 85
  25. 39
  26. 525
  27. 77
  28. 42
  29. 83
  30. 340
  31. 65
  32. 210
  33. 408
  34. 484
  35. 25
  36. 49
  37. 52
  38. 59
  39. 42
  40. 77

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