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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 295 · 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. 1.70 + 9 =
  2. 2.71 − 29 =
  3. 3.36 + 19 =
  4. 4.59 + 29 =
  5. 5.80 + 9 =
  6. 6.34 + 29 =
  7. 7.24 − 19 =
  8. 8.78 + 29 =
  9. 9.91 − 29 =
  10. 10.717 + 99 =
  11. 11.31 − 9 =
  12. 12.342 + 99 =
  13. 13.44 + 19 =
  14. 14.167 + 99 =
  15. 15.25 − 19 =
  16. 16.61 − 9 =
  17. 17.64 + 9 =
  18. 18.15 + 9 =
  19. 19.40 + 9 =
  20. 20.53 + 9 =
  21. 21.425 − 99 =
  22. 22.455 − 99 =
  23. 23.47 − 29 =
  24. 24.603 − 99 =
  25. 25.370 − 99 =
  26. 26.860 − 99 =
  27. 27.223 − 99 =
  28. 28.65 − 19 =
  29. 29.93 − 19 =
  30. 30.73 − 29 =
  31. 31.40 + 29 =
  32. 32.63 + 9 =
  33. 33.498 − 99 =
  34. 34.60 + 29 =
  35. 35.63 − 19 =
  36. 36.31 − 19 =
  37. 37.47 + 29 =
  38. 38.17 − 9 =
  39. 39.92 − 19 =
  40. 40.98 − 19 =

Answer key

  1. 79
  2. 42
  3. 55
  4. 88
  5. 89
  6. 63
  7. 5
  8. 107
  9. 62
  10. 816
  11. 22
  12. 441
  13. 63
  14. 266
  15. 6
  16. 52
  17. 73
  18. 24
  19. 49
  20. 62
  21. 326
  22. 356
  23. 18
  24. 504
  25. 271
  26. 761
  27. 124
  28. 46
  29. 74
  30. 44
  31. 69
  32. 72
  33. 399
  34. 89
  35. 44
  36. 12
  37. 76
  38. 8
  39. 73
  40. 79

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