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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 487 · 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. 1.27 + 9 =
  2. 2.37 + 9 =
  3. 3.51 + 29 =
  4. 4.30 − 9 =
  5. 5.58 − 19 =
  6. 6.238 + 99 =
  7. 7.358 − 99 =
  8. 8.19 − 9 =
  9. 9.62 + 19 =
  10. 10.25 + 29 =
  11. 11.195 − 99 =
  12. 12.598 + 99 =
  13. 13.830 − 99 =
  14. 14.45 − 9 =
  15. 15.40 + 9 =
  16. 16.31 + 9 =
  17. 17.74 − 9 =
  18. 18.54 − 19 =
  19. 19.345 + 99 =
  20. 20.29 − 9 =
  21. 21.81 − 9 =
  22. 22.60 + 29 =
  23. 23.360 + 99 =
  24. 24.45 + 9 =
  25. 25.466 + 99 =
  26. 26.86 − 19 =
  27. 27.17 + 9 =
  28. 28.203 − 99 =
  29. 29.40 + 29 =
  30. 30.21 − 9 =
  31. 31.74 + 9 =
  32. 32.12 − 9 =
  33. 33.104 − 29 =
  34. 34.74 − 19 =
  35. 35.44 + 19 =
  36. 36.56 − 29 =
  37. 37.441 − 99 =
  38. 38.71 + 29 =
  39. 39.80 + 19 =
  40. 40.19 + 29 =

Answer key

  1. 36
  2. 46
  3. 80
  4. 21
  5. 39
  6. 337
  7. 259
  8. 10
  9. 81
  10. 54
  11. 96
  12. 697
  13. 731
  14. 36
  15. 49
  16. 40
  17. 65
  18. 35
  19. 444
  20. 20
  21. 72
  22. 89
  23. 459
  24. 54
  25. 565
  26. 67
  27. 26
  28. 104
  29. 69
  30. 12
  31. 83
  32. 3
  33. 75
  34. 55
  35. 63
  36. 27
  37. 342
  38. 100
  39. 99
  40. 48

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