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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 786 · 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. 1.17 + 9 =
  2. 2.25 − 9 =
  3. 3.103 − 29 =
  4. 4.78 + 9 =
  5. 5.52 − 9 =
  6. 6.618 + 99 =
  7. 7.571 − 99 =
  8. 8.74 + 9 =
  9. 9.33 − 19 =
  10. 10.44 − 19 =
  11. 11.48 + 9 =
  12. 12.617 − 99 =
  13. 13.12 + 9 =
  14. 14.20 + 19 =
  15. 15.17 + 19 =
  16. 16.420 − 99 =
  17. 17.35 + 29 =
  18. 18.526 − 99 =
  19. 19.60 + 19 =
  20. 20.52 − 19 =
  21. 21.564 + 99 =
  22. 22.495 − 99 =
  23. 23.75 − 9 =
  24. 24.24 − 9 =
  25. 25.260 + 99 =
  26. 26.42 − 29 =
  27. 27.38 + 19 =
  28. 28.30 − 9 =
  29. 29.75 − 19 =
  30. 30.28 + 9 =
  31. 31.189 + 99 =
  32. 32.664 + 99 =
  33. 33.28 − 19 =
  34. 34.515 + 99 =
  35. 35.76 + 29 =
  36. 36.43 + 29 =
  37. 37.32 + 19 =
  38. 38.79 − 9 =
  39. 39.59 + 29 =
  40. 40.15 + 9 =

Answer key

  1. 26
  2. 16
  3. 74
  4. 87
  5. 43
  6. 717
  7. 472
  8. 83
  9. 14
  10. 25
  11. 57
  12. 518
  13. 21
  14. 39
  15. 36
  16. 321
  17. 64
  18. 427
  19. 79
  20. 33
  21. 663
  22. 396
  23. 66
  24. 15
  25. 359
  26. 13
  27. 57
  28. 21
  29. 56
  30. 37
  31. 288
  32. 763
  33. 9
  34. 614
  35. 105
  36. 72
  37. 51
  38. 70
  39. 88
  40. 24

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