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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 386 · 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. 1.52 + 9 =
  2. 2.43 − 9 =
  3. 3.21 + 9 =
  4. 4.79 − 19 =
  5. 5.107 − 29 =
  6. 6.24 + 19 =
  7. 7.26 + 9 =
  8. 8.758 + 99 =
  9. 9.40 + 19 =
  10. 10.27 + 9 =
  11. 11.21 + 19 =
  12. 12.12 + 19 =
  13. 13.19 + 29 =
  14. 14.40 + 29 =
  15. 15.56 + 19 =
  16. 16.39 − 19 =
  17. 17.181 − 99 =
  18. 18.58 − 9 =
  19. 19.68 − 9 =
  20. 20.717 + 99 =
  21. 21.16 + 29 =
  22. 22.138 + 99 =
  23. 23.625 − 99 =
  24. 24.88 − 9 =
  25. 25.172 − 99 =
  26. 26.573 + 99 =
  27. 27.291 − 99 =
  28. 28.714 + 99 =
  29. 29.70 + 29 =
  30. 30.68 + 19 =
  31. 31.32 + 29 =
  32. 32.79 + 9 =
  33. 33.60 − 9 =
  34. 34.29 + 9 =
  35. 35.19 + 19 =
  36. 36.32 + 9 =
  37. 37.22 + 9 =
  38. 38.290 − 99 =
  39. 39.361 + 99 =
  40. 40.19 + 9 =

Answer key

  1. 61
  2. 34
  3. 30
  4. 60
  5. 78
  6. 43
  7. 35
  8. 857
  9. 59
  10. 36
  11. 40
  12. 31
  13. 48
  14. 69
  15. 75
  16. 20
  17. 82
  18. 49
  19. 59
  20. 816
  21. 45
  22. 237
  23. 526
  24. 79
  25. 73
  26. 672
  27. 192
  28. 813
  29. 99
  30. 87
  31. 61
  32. 88
  33. 51
  34. 38
  35. 38
  36. 41
  37. 31
  38. 191
  39. 460
  40. 28

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