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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 381 · 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. 1.754 − 99 =
  2. 2.203 + 99 =
  3. 3.23 + 9 =
  4. 4.46 − 19 =
  5. 5.68 − 9 =
  6. 6.661 + 99 =
  7. 7.32 − 9 =
  8. 8.15 + 9 =
  9. 9.76 − 9 =
  10. 10.67 − 9 =
  11. 11.66 + 19 =
  12. 12.321 − 99 =
  13. 13.162 + 99 =
  14. 14.106 − 29 =
  15. 15.71 − 29 =
  16. 16.38 + 29 =
  17. 17.68 + 29 =
  18. 18.22 − 9 =
  19. 19.413 + 99 =
  20. 20.52 + 19 =
  21. 21.46 − 9 =
  22. 22.64 + 19 =
  23. 23.45 + 29 =
  24. 24.132 + 99 =
  25. 25.76 − 19 =
  26. 26.16 + 29 =
  27. 27.72 + 19 =
  28. 28.45 − 29 =
  29. 29.22 − 19 =
  30. 30.23 + 19 =
  31. 31.37 + 9 =
  32. 32.48 + 29 =
  33. 33.25 + 9 =
  34. 34.65 + 9 =
  35. 35.168 + 99 =
  36. 36.29 − 9 =
  37. 37.42 − 9 =
  38. 38.15 − 9 =
  39. 39.54 + 19 =
  40. 40.28 + 29 =

Answer key

  1. 655
  2. 302
  3. 32
  4. 27
  5. 59
  6. 760
  7. 23
  8. 24
  9. 67
  10. 58
  11. 85
  12. 222
  13. 261
  14. 77
  15. 42
  16. 67
  17. 97
  18. 13
  19. 512
  20. 71
  21. 37
  22. 83
  23. 74
  24. 231
  25. 57
  26. 45
  27. 91
  28. 16
  29. 3
  30. 42
  31. 46
  32. 77
  33. 34
  34. 74
  35. 267
  36. 20
  37. 33
  38. 6
  39. 73
  40. 57

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