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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 418 · 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. 1.41 − 19 =
  2. 2.71 + 29 =
  3. 3.798 − 99 =
  4. 4.69 − 19 =
  5. 5.17 + 9 =
  6. 6.63 + 19 =
  7. 7.16 + 29 =
  8. 8.35 + 9 =
  9. 9.56 + 29 =
  10. 10.281 + 99 =
  11. 11.78 + 19 =
  12. 12.46 + 9 =
  13. 13.373 + 99 =
  14. 14.43 − 29 =
  15. 15.46 − 29 =
  16. 16.48 − 29 =
  17. 17.15 + 9 =
  18. 18.54 − 9 =
  19. 19.58 − 19 =
  20. 20.38 + 9 =
  21. 21.57 + 19 =
  22. 22.42 − 9 =
  23. 23.66 − 9 =
  24. 24.192 + 99 =
  25. 25.68 + 29 =
  26. 26.591 − 99 =
  27. 27.50 − 19 =
  28. 28.55 − 9 =
  29. 29.739 + 99 =
  30. 30.100 − 29 =
  31. 31.39 + 9 =
  32. 32.285 + 99 =
  33. 33.31 − 19 =
  34. 34.265 − 99 =
  35. 35.45 − 9 =
  36. 36.247 − 99 =
  37. 37.72 + 9 =
  38. 38.28 + 29 =
  39. 39.565 − 99 =
  40. 40.36 + 29 =

Answer key

  1. 22
  2. 100
  3. 699
  4. 50
  5. 26
  6. 82
  7. 45
  8. 44
  9. 85
  10. 380
  11. 97
  12. 55
  13. 472
  14. 14
  15. 17
  16. 19
  17. 24
  18. 45
  19. 39
  20. 47
  21. 76
  22. 33
  23. 57
  24. 291
  25. 97
  26. 492
  27. 31
  28. 46
  29. 838
  30. 71
  31. 48
  32. 384
  33. 12
  34. 166
  35. 36
  36. 148
  37. 81
  38. 57
  39. 466
  40. 65

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