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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 145 · 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. 1.232 + 99 =
  2. 2.50 + 19 =
  3. 3.685 − 99 =
  4. 4.34 + 19 =
  5. 5.165 − 99 =
  6. 6.517 − 99 =
  7. 7.31 + 19 =
  8. 8.171 − 99 =
  9. 9.302 − 99 =
  10. 10.73 + 29 =
  11. 11.35 + 9 =
  12. 12.67 + 9 =
  13. 13.87 − 9 =
  14. 14.32 + 29 =
  15. 15.61 + 9 =
  16. 16.144 + 99 =
  17. 17.94 − 19 =
  18. 18.55 − 29 =
  19. 19.73 − 9 =
  20. 20.59 + 19 =
  21. 21.107 − 29 =
  22. 22.279 − 99 =
  23. 23.26 − 9 =
  24. 24.734 + 99 =
  25. 25.672 + 99 =
  26. 26.333 − 99 =
  27. 27.80 + 19 =
  28. 28.13 + 19 =
  29. 29.29 − 9 =
  30. 30.25 + 9 =
  31. 31.80 − 19 =
  32. 32.50 − 19 =
  33. 33.21 − 9 =
  34. 34.39 + 19 =
  35. 35.31 − 19 =
  36. 36.436 + 99 =
  37. 37.38 − 19 =
  38. 38.63 + 19 =
  39. 39.25 + 29 =
  40. 40.55 + 19 =

Answer key

  1. 331
  2. 69
  3. 586
  4. 53
  5. 66
  6. 418
  7. 50
  8. 72
  9. 203
  10. 102
  11. 44
  12. 76
  13. 78
  14. 61
  15. 70
  16. 243
  17. 75
  18. 26
  19. 64
  20. 78
  21. 78
  22. 180
  23. 17
  24. 833
  25. 771
  26. 234
  27. 99
  28. 32
  29. 20
  30. 34
  31. 61
  32. 31
  33. 12
  34. 58
  35. 12
  36. 535
  37. 19
  38. 82
  39. 54
  40. 74

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