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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 267 · 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. 1.23 + 19 =
  2. 2.51 + 29 =
  3. 3.16 + 29 =
  4. 4.34 + 29 =
  5. 5.70 − 9 =
  6. 6.83 − 29 =
  7. 7.44 + 9 =
  8. 8.18 + 19 =
  9. 9.15 − 9 =
  10. 10.75 + 9 =
  11. 11.77 + 9 =
  12. 12.60 + 29 =
  13. 13.247 + 99 =
  14. 14.306 + 99 =
  15. 15.33 + 9 =
  16. 16.15 + 29 =
  17. 17.64 − 19 =
  18. 18.19 + 29 =
  19. 19.48 − 9 =
  20. 20.32 + 29 =
  21. 21.362 − 99 =
  22. 22.94 − 19 =
  23. 23.94 − 29 =
  24. 24.210 + 99 =
  25. 25.832 − 99 =
  26. 26.61 + 19 =
  27. 27.78 − 29 =
  28. 28.77 − 9 =
  29. 29.42 + 9 =
  30. 30.73 − 19 =
  31. 31.44 − 19 =
  32. 32.96 − 29 =
  33. 33.25 − 9 =
  34. 34.22 + 19 =
  35. 35.896 − 99 =
  36. 36.15 + 9 =
  37. 37.101 − 29 =
  38. 38.78 + 29 =
  39. 39.45 − 29 =
  40. 40.65 + 29 =

Answer key

  1. 42
  2. 80
  3. 45
  4. 63
  5. 61
  6. 54
  7. 53
  8. 37
  9. 6
  10. 84
  11. 86
  12. 89
  13. 346
  14. 405
  15. 42
  16. 44
  17. 45
  18. 48
  19. 39
  20. 61
  21. 263
  22. 75
  23. 65
  24. 309
  25. 733
  26. 80
  27. 49
  28. 68
  29. 51
  30. 54
  31. 25
  32. 67
  33. 16
  34. 41
  35. 797
  36. 24
  37. 72
  38. 107
  39. 16
  40. 94

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