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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 98 · 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. 1.109 − 29 =
  2. 2.30 + 19 =
  3. 3.16 + 9 =
  4. 4.78 + 9 =
  5. 5.178 − 99 =
  6. 6.27 + 29 =
  7. 7.22 − 19 =
  8. 8.714 − 99 =
  9. 9.67 − 9 =
  10. 10.275 − 99 =
  11. 11.39 + 19 =
  12. 12.63 − 29 =
  13. 13.15 + 19 =
  14. 14.54 − 29 =
  15. 15.41 − 29 =
  16. 16.60 + 9 =
  17. 17.75 + 9 =
  18. 18.67 + 29 =
  19. 19.47 + 19 =
  20. 20.80 − 29 =
  21. 21.53 − 29 =
  22. 22.15 + 29 =
  23. 23.46 + 19 =
  24. 24.380 − 99 =
  25. 25.35 + 29 =
  26. 26.29 − 9 =
  27. 27.38 + 29 =
  28. 28.65 − 9 =
  29. 29.67 + 19 =
  30. 30.59 − 19 =
  31. 31.894 − 99 =
  32. 32.64 − 9 =
  33. 33.37 + 19 =
  34. 34.24 + 9 =
  35. 35.252 − 99 =
  36. 36.74 + 29 =
  37. 37.66 + 29 =
  38. 38.77 − 29 =
  39. 39.601 − 99 =
  40. 40.361 − 99 =

Answer key

  1. 80
  2. 49
  3. 25
  4. 87
  5. 79
  6. 56
  7. 3
  8. 615
  9. 58
  10. 176
  11. 58
  12. 34
  13. 34
  14. 25
  15. 12
  16. 69
  17. 84
  18. 96
  19. 66
  20. 51
  21. 24
  22. 44
  23. 65
  24. 281
  25. 64
  26. 20
  27. 67
  28. 56
  29. 86
  30. 40
  31. 795
  32. 55
  33. 56
  34. 33
  35. 153
  36. 103
  37. 95
  38. 48
  39. 502
  40. 262

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