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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 614 · 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. 1.62 − 9 =
  2. 2.30 − 9 =
  3. 3.43 + 29 =
  4. 4.411 − 99 =
  5. 5.65 + 29 =
  6. 6.79 − 19 =
  7. 7.253 − 99 =
  8. 8.22 + 29 =
  9. 9.246 − 99 =
  10. 10.610 − 99 =
  11. 11.47 − 29 =
  12. 12.32 − 19 =
  13. 13.94 − 29 =
  14. 14.893 − 99 =
  15. 15.51 − 19 =
  16. 16.39 + 29 =
  17. 17.45 − 29 =
  18. 18.26 + 19 =
  19. 19.33 + 19 =
  20. 20.29 + 19 =
  21. 21.77 + 9 =
  22. 22.178 + 99 =
  23. 23.855 − 99 =
  24. 24.19 + 29 =
  25. 25.89 − 9 =
  26. 26.48 − 9 =
  27. 27.74 + 9 =
  28. 28.50 − 19 =
  29. 29.83 − 19 =
  30. 30.26 − 19 =
  31. 31.258 − 99 =
  32. 32.77 − 9 =
  33. 33.325 + 99 =
  34. 34.55 − 9 =
  35. 35.538 + 99 =
  36. 36.24 − 19 =
  37. 37.58 + 29 =
  38. 38.64 + 29 =
  39. 39.236 + 99 =
  40. 40.75 − 29 =

Answer key

  1. 53
  2. 21
  3. 72
  4. 312
  5. 94
  6. 60
  7. 154
  8. 51
  9. 147
  10. 511
  11. 18
  12. 13
  13. 65
  14. 794
  15. 32
  16. 68
  17. 16
  18. 45
  19. 52
  20. 48
  21. 86
  22. 277
  23. 756
  24. 48
  25. 80
  26. 39
  27. 83
  28. 31
  29. 64
  30. 7
  31. 159
  32. 68
  33. 424
  34. 46
  35. 637
  36. 5
  37. 87
  38. 93
  39. 335
  40. 46

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