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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 158 · 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. 1.374 + 99 =
  2. 2.68 + 9 =
  3. 3.59 + 19 =
  4. 4.63 + 29 =
  5. 5.68 − 19 =
  6. 6.220 + 99 =
  7. 7.66 + 9 =
  8. 8.884 − 99 =
  9. 9.184 + 99 =
  10. 10.221 − 99 =
  11. 11.40 − 9 =
  12. 12.41 − 29 =
  13. 13.51 + 19 =
  14. 14.85 − 19 =
  15. 15.80 − 29 =
  16. 16.35 + 29 =
  17. 17.81 − 29 =
  18. 18.23 + 19 =
  19. 19.67 + 29 =
  20. 20.25 − 19 =
  21. 21.109 + 99 =
  22. 22.27 + 9 =
  23. 23.40 − 29 =
  24. 24.49 + 19 =
  25. 25.24 − 19 =
  26. 26.56 − 9 =
  27. 27.15 − 9 =
  28. 28.526 − 99 =
  29. 29.119 + 99 =
  30. 30.30 + 19 =
  31. 31.56 + 19 =
  32. 32.64 + 19 =
  33. 33.22 + 9 =
  34. 34.17 + 19 =
  35. 35.92 − 19 =
  36. 36.540 + 99 =
  37. 37.171 − 99 =
  38. 38.306 + 99 =
  39. 39.74 + 29 =
  40. 40.42 + 9 =

Answer key

  1. 473
  2. 77
  3. 78
  4. 92
  5. 49
  6. 319
  7. 75
  8. 785
  9. 283
  10. 122
  11. 31
  12. 12
  13. 70
  14. 66
  15. 51
  16. 64
  17. 52
  18. 42
  19. 96
  20. 6
  21. 208
  22. 36
  23. 11
  24. 68
  25. 5
  26. 47
  27. 6
  28. 427
  29. 218
  30. 49
  31. 75
  32. 83
  33. 31
  34. 36
  35. 73
  36. 639
  37. 72
  38. 405
  39. 103
  40. 51

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