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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 91 · 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. 1.21 + 29 =
  2. 2.68 + 19 =
  3. 3.78 + 19 =
  4. 4.247 + 99 =
  5. 5.35 + 9 =
  6. 6.53 − 19 =
  7. 7.49 + 29 =
  8. 8.36 + 19 =
  9. 9.79 + 29 =
  10. 10.87 − 9 =
  11. 11.69 + 19 =
  12. 12.18 + 19 =
  13. 13.17 + 9 =
  14. 14.31 + 19 =
  15. 15.54 + 29 =
  16. 16.34 + 9 =
  17. 17.78 − 19 =
  18. 18.413 + 99 =
  19. 19.454 + 99 =
  20. 20.85 − 9 =
  21. 21.75 − 29 =
  22. 22.70 + 29 =
  23. 23.42 + 29 =
  24. 24.461 − 99 =
  25. 25.12 + 9 =
  26. 26.19 + 9 =
  27. 27.98 − 19 =
  28. 28.24 + 29 =
  29. 29.402 − 99 =
  30. 30.43 + 19 =
  31. 31.53 + 29 =
  32. 32.27 + 19 =
  33. 33.16 + 29 =
  34. 34.65 − 19 =
  35. 35.12 + 29 =
  36. 36.55 − 29 =
  37. 37.49 − 29 =
  38. 38.70 + 9 =
  39. 39.79 − 19 =
  40. 40.160 + 99 =

Answer key

  1. 50
  2. 87
  3. 97
  4. 346
  5. 44
  6. 34
  7. 78
  8. 55
  9. 108
  10. 78
  11. 88
  12. 37
  13. 26
  14. 50
  15. 83
  16. 43
  17. 59
  18. 512
  19. 553
  20. 76
  21. 46
  22. 99
  23. 71
  24. 362
  25. 21
  26. 28
  27. 79
  28. 53
  29. 303
  30. 62
  31. 82
  32. 46
  33. 45
  34. 46
  35. 41
  36. 26
  37. 20
  38. 79
  39. 60
  40. 259

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