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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 299 · 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. 1.28 − 9 =
  2. 2.55 − 9 =
  3. 3.65 − 9 =
  4. 4.69 − 9 =
  5. 5.283 + 99 =
  6. 6.38 + 29 =
  7. 7.79 − 9 =
  8. 8.46 + 29 =
  9. 9.197 − 99 =
  10. 10.863 − 99 =
  11. 11.425 + 99 =
  12. 12.64 + 19 =
  13. 13.26 + 29 =
  14. 14.497 + 99 =
  15. 15.29 + 19 =
  16. 16.59 − 29 =
  17. 17.84 − 9 =
  18. 18.35 + 19 =
  19. 19.96 − 29 =
  20. 20.34 + 29 =
  21. 21.54 − 29 =
  22. 22.44 − 9 =
  23. 23.26 − 9 =
  24. 24.272 + 99 =
  25. 25.23 + 19 =
  26. 26.76 + 29 =
  27. 27.52 + 9 =
  28. 28.56 + 29 =
  29. 29.28 + 9 =
  30. 30.66 − 9 =
  31. 31.72 − 29 =
  32. 32.35 + 29 =
  33. 33.37 + 29 =
  34. 34.27 − 19 =
  35. 35.169 − 99 =
  36. 36.506 + 99 =
  37. 37.55 + 9 =
  38. 38.76 − 19 =
  39. 39.38 − 19 =
  40. 40.209 + 99 =

Answer key

  1. 19
  2. 46
  3. 56
  4. 60
  5. 382
  6. 67
  7. 70
  8. 75
  9. 98
  10. 764
  11. 524
  12. 83
  13. 55
  14. 596
  15. 48
  16. 30
  17. 75
  18. 54
  19. 67
  20. 63
  21. 25
  22. 35
  23. 17
  24. 371
  25. 42
  26. 105
  27. 61
  28. 85
  29. 37
  30. 57
  31. 43
  32. 64
  33. 66
  34. 8
  35. 70
  36. 605
  37. 64
  38. 57
  39. 19
  40. 308

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