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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 239 · 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. 1.80 + 29 =
  2. 2.78 − 19 =
  3. 3.13 + 9 =
  4. 4.91 − 19 =
  5. 5.277 + 99 =
  6. 6.70 − 29 =
  7. 7.44 + 29 =
  8. 8.66 − 29 =
  9. 9.21 + 9 =
  10. 10.64 + 9 =
  11. 11.82 − 19 =
  12. 12.96 − 19 =
  13. 13.87 − 19 =
  14. 14.55 + 9 =
  15. 15.356 − 99 =
  16. 16.27 − 9 =
  17. 17.64 + 19 =
  18. 18.686 + 99 =
  19. 19.357 − 99 =
  20. 20.19 + 29 =
  21. 21.46 + 29 =
  22. 22.73 + 19 =
  23. 23.585 + 99 =
  24. 24.257 + 99 =
  25. 25.22 + 29 =
  26. 26.261 + 99 =
  27. 27.60 + 29 =
  28. 28.53 − 9 =
  29. 29.88 − 9 =
  30. 30.42 − 29 =
  31. 31.68 − 19 =
  32. 32.46 + 19 =
  33. 33.82 − 9 =
  34. 34.42 − 9 =
  35. 35.31 − 9 =
  36. 36.76 − 9 =
  37. 37.98 − 29 =
  38. 38.92 − 19 =
  39. 39.22 + 19 =
  40. 40.664 − 99 =

Answer key

  1. 109
  2. 59
  3. 22
  4. 72
  5. 376
  6. 41
  7. 73
  8. 37
  9. 30
  10. 73
  11. 63
  12. 77
  13. 68
  14. 64
  15. 257
  16. 18
  17. 83
  18. 785
  19. 258
  20. 48
  21. 75
  22. 92
  23. 684
  24. 356
  25. 51
  26. 360
  27. 89
  28. 44
  29. 79
  30. 13
  31. 49
  32. 65
  33. 73
  34. 33
  35. 22
  36. 67
  37. 69
  38. 73
  39. 41
  40. 565

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