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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 147 · 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. 1.22 + 19 =
  2. 2.101 − 29 =
  3. 3.59 + 29 =
  4. 4.84 − 29 =
  5. 5.87 − 9 =
  6. 6.51 − 29 =
  7. 7.175 + 99 =
  8. 8.186 + 99 =
  9. 9.42 − 9 =
  10. 10.39 + 9 =
  11. 11.57 + 29 =
  12. 12.134 + 99 =
  13. 13.49 + 19 =
  14. 14.348 − 99 =
  15. 15.104 − 29 =
  16. 16.208 − 99 =
  17. 17.31 + 19 =
  18. 18.65 + 19 =
  19. 19.20 + 29 =
  20. 20.49 + 29 =
  21. 21.58 − 9 =
  22. 22.75 + 29 =
  23. 23.61 + 29 =
  24. 24.21 + 9 =
  25. 25.25 + 29 =
  26. 26.22 + 29 =
  27. 27.812 − 99 =
  28. 28.45 + 29 =
  29. 29.18 + 19 =
  30. 30.33 − 9 =
  31. 31.17 + 19 =
  32. 32.47 + 9 =
  33. 33.47 + 19 =
  34. 34.15 − 9 =
  35. 35.30 − 9 =
  36. 36.50 + 9 =
  37. 37.12 − 9 =
  38. 38.808 − 99 =
  39. 39.218 + 99 =
  40. 40.63 − 9 =

Answer key

  1. 41
  2. 72
  3. 88
  4. 55
  5. 78
  6. 22
  7. 274
  8. 285
  9. 33
  10. 48
  11. 86
  12. 233
  13. 68
  14. 249
  15. 75
  16. 109
  17. 50
  18. 84
  19. 49
  20. 78
  21. 49
  22. 104
  23. 90
  24. 30
  25. 54
  26. 51
  27. 713
  28. 74
  29. 37
  30. 24
  31. 36
  32. 56
  33. 66
  34. 6
  35. 21
  36. 59
  37. 3
  38. 709
  39. 317
  40. 54

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