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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 46 · 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. 1.20 + 9 =
  2. 2.212 + 99 =
  3. 3.78 − 29 =
  4. 4.281 + 99 =
  5. 5.25 + 9 =
  6. 6.89 − 19 =
  7. 7.69 + 29 =
  8. 8.606 + 99 =
  9. 9.180 − 99 =
  10. 10.770 + 99 =
  11. 11.59 + 29 =
  12. 12.86 − 29 =
  13. 13.749 − 99 =
  14. 14.53 + 19 =
  15. 15.26 − 19 =
  16. 16.43 + 29 =
  17. 17.61 + 9 =
  18. 18.77 + 9 =
  19. 19.79 + 29 =
  20. 20.294 + 99 =
  21. 21.12 + 9 =
  22. 22.28 + 19 =
  23. 23.99 − 19 =
  24. 24.58 + 19 =
  25. 25.41 + 19 =
  26. 26.21 + 9 =
  27. 27.43 − 29 =
  28. 28.89 − 9 =
  29. 29.49 + 19 =
  30. 30.220 − 99 =
  31. 31.68 − 9 =
  32. 32.40 − 19 =
  33. 33.51 + 29 =
  34. 34.66 − 29 =
  35. 35.57 − 29 =
  36. 36.389 + 99 =
  37. 37.29 − 19 =
  38. 38.35 + 29 =
  39. 39.469 + 99 =
  40. 40.33 + 19 =

Answer key

  1. 29
  2. 311
  3. 49
  4. 380
  5. 34
  6. 70
  7. 98
  8. 705
  9. 81
  10. 869
  11. 88
  12. 57
  13. 650
  14. 72
  15. 7
  16. 72
  17. 70
  18. 86
  19. 108
  20. 393
  21. 21
  22. 47
  23. 80
  24. 77
  25. 60
  26. 30
  27. 14
  28. 80
  29. 68
  30. 121
  31. 59
  32. 21
  33. 80
  34. 37
  35. 28
  36. 488
  37. 10
  38. 64
  39. 568
  40. 52

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