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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 372 · 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. 1.191 + 99 =
  2. 2.61 + 29 =
  3. 3.180 − 99 =
  4. 4.77 + 29 =
  5. 5.75 − 19 =
  6. 6.52 + 9 =
  7. 7.23 + 29 =
  8. 8.31 − 19 =
  9. 9.44 + 29 =
  10. 10.423 + 99 =
  11. 11.16 + 9 =
  12. 12.56 + 29 =
  13. 13.428 + 99 =
  14. 14.58 + 19 =
  15. 15.74 + 9 =
  16. 16.50 + 9 =
  17. 17.54 − 19 =
  18. 18.44 − 9 =
  19. 19.46 + 29 =
  20. 20.80 − 19 =
  21. 21.425 + 99 =
  22. 22.48 − 9 =
  23. 23.135 + 99 =
  24. 24.558 − 99 =
  25. 25.171 + 99 =
  26. 26.40 + 29 =
  27. 27.58 + 9 =
  28. 28.83 − 9 =
  29. 29.79 + 29 =
  30. 30.78 − 29 =
  31. 31.18 + 19 =
  32. 32.26 − 9 =
  33. 33.66 − 29 =
  34. 34.361 − 99 =
  35. 35.72 − 29 =
  36. 36.453 + 99 =
  37. 37.66 + 29 =
  38. 38.61 + 19 =
  39. 39.93 − 29 =
  40. 40.43 + 9 =

Answer key

  1. 290
  2. 90
  3. 81
  4. 106
  5. 56
  6. 61
  7. 52
  8. 12
  9. 73
  10. 522
  11. 25
  12. 85
  13. 527
  14. 77
  15. 83
  16. 59
  17. 35
  18. 35
  19. 75
  20. 61
  21. 524
  22. 39
  23. 234
  24. 459
  25. 270
  26. 69
  27. 67
  28. 74
  29. 108
  30. 49
  31. 37
  32. 17
  33. 37
  34. 262
  35. 43
  36. 552
  37. 95
  38. 80
  39. 64
  40. 52

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