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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 880 · 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. 1.38 + 9 =
  2. 2.50 + 29 =
  3. 3.66 + 29 =
  4. 4.61 − 19 =
  5. 5.629 − 99 =
  6. 6.517 − 99 =
  7. 7.17 − 9 =
  8. 8.569 + 99 =
  9. 9.78 + 9 =
  10. 10.33 − 29 =
  11. 11.65 + 29 =
  12. 12.174 + 99 =
  13. 13.563 + 99 =
  14. 14.46 + 19 =
  15. 15.82 − 19 =
  16. 16.581 + 99 =
  17. 17.57 + 19 =
  18. 18.644 − 99 =
  19. 19.50 − 9 =
  20. 20.38 + 29 =
  21. 21.150 − 99 =
  22. 22.31 − 9 =
  23. 23.66 − 29 =
  24. 24.40 + 19 =
  25. 25.30 + 9 =
  26. 26.33 − 9 =
  27. 27.34 − 29 =
  28. 28.52 − 19 =
  29. 29.60 − 29 =
  30. 30.27 − 19 =
  31. 31.555 + 99 =
  32. 32.769 − 99 =
  33. 33.522 − 99 =
  34. 34.78 − 9 =
  35. 35.27 + 29 =
  36. 36.45 + 19 =
  37. 37.144 + 99 =
  38. 38.258 − 99 =
  39. 39.49 − 29 =
  40. 40.48 + 29 =

Answer key

  1. 47
  2. 79
  3. 95
  4. 42
  5. 530
  6. 418
  7. 8
  8. 668
  9. 87
  10. 4
  11. 94
  12. 273
  13. 662
  14. 65
  15. 63
  16. 680
  17. 76
  18. 545
  19. 41
  20. 67
  21. 51
  22. 22
  23. 37
  24. 59
  25. 39
  26. 24
  27. 5
  28. 33
  29. 31
  30. 8
  31. 654
  32. 670
  33. 423
  34. 69
  35. 56
  36. 64
  37. 243
  38. 159
  39. 20
  40. 77

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