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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 275 · 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. 1.57 + 19 =
  2. 2.20 + 9 =
  3. 3.30 + 29 =
  4. 4.81 − 29 =
  5. 5.449 − 99 =
  6. 6.56 − 19 =
  7. 7.666 + 99 =
  8. 8.25 − 9 =
  9. 9.62 + 9 =
  10. 10.30 − 9 =
  11. 11.25 + 19 =
  12. 12.252 + 99 =
  13. 13.36 − 9 =
  14. 14.576 + 99 =
  15. 15.21 + 19 =
  16. 16.46 − 29 =
  17. 17.68 + 29 =
  18. 18.281 − 99 =
  19. 19.71 + 19 =
  20. 20.65 + 19 =
  21. 21.40 + 19 =
  22. 22.73 + 29 =
  23. 23.35 − 19 =
  24. 24.85 − 9 =
  25. 25.287 − 99 =
  26. 26.581 − 99 =
  27. 27.29 + 9 =
  28. 28.38 − 29 =
  29. 29.65 + 29 =
  30. 30.163 + 99 =
  31. 31.20 + 29 =
  32. 32.45 − 19 =
  33. 33.41 − 19 =
  34. 34.457 + 99 =
  35. 35.34 + 29 =
  36. 36.48 + 19 =
  37. 37.63 + 9 =
  38. 38.61 + 9 =
  39. 39.41 − 29 =
  40. 40.514 + 99 =

Answer key

  1. 76
  2. 29
  3. 59
  4. 52
  5. 350
  6. 37
  7. 765
  8. 16
  9. 71
  10. 21
  11. 44
  12. 351
  13. 27
  14. 675
  15. 40
  16. 17
  17. 97
  18. 182
  19. 90
  20. 84
  21. 59
  22. 102
  23. 16
  24. 76
  25. 188
  26. 482
  27. 38
  28. 9
  29. 94
  30. 262
  31. 49
  32. 26
  33. 22
  34. 556
  35. 63
  36. 67
  37. 72
  38. 70
  39. 12
  40. 613

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