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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 31 · 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. 1.26 + 9 =
  2. 2.575 + 99 =
  3. 3.325 − 99 =
  4. 4.25 − 19 =
  5. 5.15 + 29 =
  6. 6.18 + 9 =
  7. 7.548 − 99 =
  8. 8.18 − 9 =
  9. 9.98 − 29 =
  10. 10.94 − 19 =
  11. 11.80 − 29 =
  12. 12.65 − 29 =
  13. 13.554 + 99 =
  14. 14.17 − 9 =
  15. 15.58 + 9 =
  16. 16.71 − 9 =
  17. 17.13 + 9 =
  18. 18.98 − 19 =
  19. 19.76 + 9 =
  20. 20.29 + 9 =
  21. 21.187 + 99 =
  22. 22.42 + 29 =
  23. 23.25 + 19 =
  24. 24.290 + 99 =
  25. 25.71 + 19 =
  26. 26.28 − 19 =
  27. 27.40 − 19 =
  28. 28.15 − 9 =
  29. 29.265 + 99 =
  30. 30.570 + 99 =
  31. 31.67 + 19 =
  32. 32.79 − 9 =
  33. 33.60 + 29 =
  34. 34.75 − 19 =
  35. 35.248 + 99 =
  36. 36.40 − 9 =
  37. 37.466 − 99 =
  38. 38.114 + 99 =
  39. 39.72 − 29 =
  40. 40.63 − 19 =

Answer key

  1. 35
  2. 674
  3. 226
  4. 6
  5. 44
  6. 27
  7. 449
  8. 9
  9. 69
  10. 75
  11. 51
  12. 36
  13. 653
  14. 8
  15. 67
  16. 62
  17. 22
  18. 79
  19. 85
  20. 38
  21. 286
  22. 71
  23. 44
  24. 389
  25. 90
  26. 9
  27. 21
  28. 6
  29. 364
  30. 669
  31. 86
  32. 70
  33. 89
  34. 56
  35. 347
  36. 31
  37. 367
  38. 213
  39. 43
  40. 44

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