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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 949 · 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. 1.366 − 99 =
  2. 2.73 + 19 =
  3. 3.374 − 99 =
  4. 4.45 + 9 =
  5. 5.350 − 99 =
  6. 6.39 − 19 =
  7. 7.36 − 19 =
  8. 8.51 − 19 =
  9. 9.28 − 19 =
  10. 10.88 − 29 =
  11. 11.46 + 19 =
  12. 12.21 + 19 =
  13. 13.66 − 19 =
  14. 14.20 − 9 =
  15. 15.57 − 19 =
  16. 16.51 − 29 =
  17. 17.57 + 9 =
  18. 18.70 − 19 =
  19. 19.28 + 9 =
  20. 20.31 + 9 =
  21. 21.210 − 99 =
  22. 22.43 + 9 =
  23. 23.59 − 29 =
  24. 24.47 + 9 =
  25. 25.82 − 29 =
  26. 26.355 + 99 =
  27. 27.548 + 99 =
  28. 28.39 + 9 =
  29. 29.67 + 9 =
  30. 30.62 + 9 =
  31. 31.27 − 9 =
  32. 32.75 − 9 =
  33. 33.75 + 29 =
  34. 34.250 + 99 =
  35. 35.43 − 19 =
  36. 36.21 − 9 =
  37. 37.109 − 29 =
  38. 38.70 + 9 =
  39. 39.54 + 19 =
  40. 40.47 + 29 =

Answer key

  1. 267
  2. 92
  3. 275
  4. 54
  5. 251
  6. 20
  7. 17
  8. 32
  9. 9
  10. 59
  11. 65
  12. 40
  13. 47
  14. 11
  15. 38
  16. 22
  17. 66
  18. 51
  19. 37
  20. 40
  21. 111
  22. 52
  23. 30
  24. 56
  25. 53
  26. 454
  27. 647
  28. 48
  29. 76
  30. 71
  31. 18
  32. 66
  33. 104
  34. 349
  35. 24
  36. 12
  37. 80
  38. 79
  39. 73
  40. 76

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