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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 206 · 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. 1.81 − 9 =
  2. 2.97 − 19 =
  3. 3.61 − 29 =
  4. 4.14 + 19 =
  5. 5.535 − 99 =
  6. 6.20 − 9 =
  7. 7.534 − 99 =
  8. 8.55 + 29 =
  9. 9.85 − 9 =
  10. 10.73 − 9 =
  11. 11.278 + 99 =
  12. 12.645 − 99 =
  13. 13.33 + 29 =
  14. 14.17 + 19 =
  15. 15.83 − 29 =
  16. 16.49 + 19 =
  17. 17.187 + 99 =
  18. 18.62 + 29 =
  19. 19.409 − 99 =
  20. 20.784 − 99 =
  21. 21.351 − 99 =
  22. 22.47 − 9 =
  23. 23.73 − 19 =
  24. 24.64 − 9 =
  25. 25.25 − 9 =
  26. 26.50 + 29 =
  27. 27.56 − 9 =
  28. 28.25 + 19 =
  29. 29.350 − 99 =
  30. 30.75 − 9 =
  31. 31.69 − 9 =
  32. 32.49 + 9 =
  33. 33.41 − 19 =
  34. 34.56 + 29 =
  35. 35.82 − 29 =
  36. 36.45 + 9 =
  37. 37.476 − 99 =
  38. 38.15 + 9 =
  39. 39.57 − 19 =
  40. 40.156 − 99 =

Answer key

  1. 72
  2. 78
  3. 32
  4. 33
  5. 436
  6. 11
  7. 435
  8. 84
  9. 76
  10. 64
  11. 377
  12. 546
  13. 62
  14. 36
  15. 54
  16. 68
  17. 286
  18. 91
  19. 310
  20. 685
  21. 252
  22. 38
  23. 54
  24. 55
  25. 16
  26. 79
  27. 47
  28. 44
  29. 251
  30. 66
  31. 60
  32. 58
  33. 22
  34. 85
  35. 53
  36. 54
  37. 377
  38. 24
  39. 38
  40. 57

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