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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 248 · 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. 1.58 + 19 =
  2. 2.46 + 9 =
  3. 3.71 − 9 =
  4. 4.39 + 9 =
  5. 5.64 + 29 =
  6. 6.67 + 29 =
  7. 7.772 + 99 =
  8. 8.411 + 99 =
  9. 9.21 + 19 =
  10. 10.17 + 19 =
  11. 11.52 + 9 =
  12. 12.50 + 19 =
  13. 13.429 + 99 =
  14. 14.93 − 29 =
  15. 15.34 − 9 =
  16. 16.108 − 29 =
  17. 17.24 + 9 =
  18. 18.17 + 29 =
  19. 19.107 + 99 =
  20. 20.73 − 29 =
  21. 21.38 + 9 =
  22. 22.65 − 29 =
  23. 23.54 − 9 =
  24. 24.266 + 99 =
  25. 25.14 − 9 =
  26. 26.77 − 19 =
  27. 27.68 + 29 =
  28. 28.49 + 9 =
  29. 29.30 − 9 =
  30. 30.19 + 29 =
  31. 31.59 + 19 =
  32. 32.43 − 29 =
  33. 33.22 + 9 =
  34. 34.16 + 29 =
  35. 35.73 + 29 =
  36. 36.883 − 99 =
  37. 37.33 − 9 =
  38. 38.18 − 9 =
  39. 39.79 − 19 =
  40. 40.36 + 9 =

Answer key

  1. 77
  2. 55
  3. 62
  4. 48
  5. 93
  6. 96
  7. 871
  8. 510
  9. 40
  10. 36
  11. 61
  12. 69
  13. 528
  14. 64
  15. 25
  16. 79
  17. 33
  18. 46
  19. 206
  20. 44
  21. 47
  22. 36
  23. 45
  24. 365
  25. 5
  26. 58
  27. 97
  28. 58
  29. 21
  30. 48
  31. 78
  32. 14
  33. 31
  34. 45
  35. 102
  36. 784
  37. 24
  38. 9
  39. 60
  40. 45

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