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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 927 · 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. 1.55 + 9 =
  2. 2.229 − 99 =
  3. 3.20 − 9 =
  4. 4.41 + 9 =
  5. 5.898 − 99 =
  6. 6.60 − 19 =
  7. 7.69 + 19 =
  8. 8.29 + 9 =
  9. 9.83 − 9 =
  10. 10.56 + 29 =
  11. 11.193 + 99 =
  12. 12.50 − 9 =
  13. 13.217 − 99 =
  14. 14.21 + 19 =
  15. 15.66 − 9 =
  16. 16.84 − 9 =
  17. 17.361 − 99 =
  18. 18.250 − 99 =
  19. 19.24 + 29 =
  20. 20.41 + 29 =
  21. 21.33 + 19 =
  22. 22.70 + 29 =
  23. 23.270 − 99 =
  24. 24.42 − 9 =
  25. 25.63 − 29 =
  26. 26.25 + 9 =
  27. 27.245 + 99 =
  28. 28.18 − 9 =
  29. 29.64 − 29 =
  30. 30.321 + 99 =
  31. 31.760 + 99 =
  32. 32.45 − 29 =
  33. 33.138 + 99 =
  34. 34.56 + 19 =
  35. 35.28 + 9 =
  36. 36.20 + 29 =
  37. 37.90 − 29 =
  38. 38.25 + 29 =
  39. 39.458 − 99 =
  40. 40.94 − 19 =

Answer key

  1. 64
  2. 130
  3. 11
  4. 50
  5. 799
  6. 41
  7. 88
  8. 38
  9. 74
  10. 85
  11. 292
  12. 41
  13. 118
  14. 40
  15. 57
  16. 75
  17. 262
  18. 151
  19. 53
  20. 70
  21. 52
  22. 99
  23. 171
  24. 33
  25. 34
  26. 34
  27. 344
  28. 9
  29. 35
  30. 420
  31. 859
  32. 16
  33. 237
  34. 75
  35. 37
  36. 49
  37. 61
  38. 54
  39. 359
  40. 75

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