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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 512 · 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. 1.18 − 9 =
  2. 2.38 + 29 =
  3. 3.30 + 19 =
  4. 4.82 − 29 =
  5. 5.549 + 99 =
  6. 6.429 + 99 =
  7. 7.22 − 19 =
  8. 8.46 − 9 =
  9. 9.74 + 19 =
  10. 10.99 − 19 =
  11. 11.55 − 29 =
  12. 12.36 + 29 =
  13. 13.38 + 19 =
  14. 14.67 + 19 =
  15. 15.22 + 29 =
  16. 16.23 + 29 =
  17. 17.495 − 99 =
  18. 18.28 + 9 =
  19. 19.82 − 19 =
  20. 20.81 − 9 =
  21. 21.416 + 99 =
  22. 22.46 + 9 =
  23. 23.708 − 99 =
  24. 24.12 + 29 =
  25. 25.76 − 9 =
  26. 26.77 + 9 =
  27. 27.86 − 29 =
  28. 28.76 + 9 =
  29. 29.32 + 19 =
  30. 30.66 − 19 =
  31. 31.74 + 29 =
  32. 32.70 + 19 =
  33. 33.80 + 29 =
  34. 34.47 + 9 =
  35. 35.88 − 29 =
  36. 36.404 − 99 =
  37. 37.23 − 9 =
  38. 38.142 + 99 =
  39. 39.17 + 29 =
  40. 40.38 − 9 =

Answer key

  1. 9
  2. 67
  3. 49
  4. 53
  5. 648
  6. 528
  7. 3
  8. 37
  9. 93
  10. 80
  11. 26
  12. 65
  13. 57
  14. 86
  15. 51
  16. 52
  17. 396
  18. 37
  19. 63
  20. 72
  21. 515
  22. 55
  23. 609
  24. 41
  25. 67
  26. 86
  27. 57
  28. 85
  29. 51
  30. 47
  31. 103
  32. 89
  33. 109
  34. 56
  35. 59
  36. 305
  37. 14
  38. 241
  39. 46
  40. 29

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