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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 592 · 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. 1.103 − 29 =
  2. 2.85 − 29 =
  3. 3.36 + 9 =
  4. 4.84 − 29 =
  5. 5.155 + 99 =
  6. 6.358 − 99 =
  7. 7.79 + 9 =
  8. 8.368 + 99 =
  9. 9.240 − 99 =
  10. 10.52 − 9 =
  11. 11.295 + 99 =
  12. 12.53 − 19 =
  13. 13.48 + 29 =
  14. 14.24 + 19 =
  15. 15.389 − 99 =
  16. 16.74 + 9 =
  17. 17.108 − 29 =
  18. 18.14 + 9 =
  19. 19.21 + 9 =
  20. 20.38 + 9 =
  21. 21.56 − 19 =
  22. 22.21 − 9 =
  23. 23.235 − 99 =
  24. 24.87 − 29 =
  25. 25.53 + 19 =
  26. 26.53 + 29 =
  27. 27.102 − 29 =
  28. 28.717 − 99 =
  29. 29.67 − 9 =
  30. 30.60 + 9 =
  31. 31.18 + 19 =
  32. 32.26 − 9 =
  33. 33.142 + 99 =
  34. 34.16 + 19 =
  35. 35.59 + 29 =
  36. 36.65 − 29 =
  37. 37.47 + 19 =
  38. 38.558 + 99 =
  39. 39.292 + 99 =
  40. 40.30 + 9 =

Answer key

  1. 74
  2. 56
  3. 45
  4. 55
  5. 254
  6. 259
  7. 88
  8. 467
  9. 141
  10. 43
  11. 394
  12. 34
  13. 77
  14. 43
  15. 290
  16. 83
  17. 79
  18. 23
  19. 30
  20. 47
  21. 37
  22. 12
  23. 136
  24. 58
  25. 72
  26. 82
  27. 73
  28. 618
  29. 58
  30. 69
  31. 37
  32. 17
  33. 241
  34. 35
  35. 88
  36. 36
  37. 66
  38. 657
  39. 391
  40. 39

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