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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 518 · 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. 1.71 − 9 =
  2. 2.93 − 19 =
  3. 3.772 + 99 =
  4. 4.37 − 29 =
  5. 5.55 + 19 =
  6. 6.39 + 29 =
  7. 7.227 − 99 =
  8. 8.44 + 29 =
  9. 9.59 − 19 =
  10. 10.34 − 29 =
  11. 11.21 + 19 =
  12. 12.72 + 29 =
  13. 13.57 + 9 =
  14. 14.29 + 9 =
  15. 15.91 − 29 =
  16. 16.35 + 9 =
  17. 17.590 + 99 =
  18. 18.40 − 9 =
  19. 19.15 + 19 =
  20. 20.25 + 29 =
  21. 21.30 − 19 =
  22. 22.60 + 9 =
  23. 23.614 + 99 =
  24. 24.840 − 99 =
  25. 25.50 − 9 =
  26. 26.376 + 99 =
  27. 27.480 + 99 =
  28. 28.102 − 29 =
  29. 29.68 − 19 =
  30. 30.53 + 19 =
  31. 31.30 + 29 =
  32. 32.64 + 9 =
  33. 33.76 − 9 =
  34. 34.85 − 29 =
  35. 35.32 − 19 =
  36. 36.45 + 19 =
  37. 37.425 + 99 =
  38. 38.22 + 29 =
  39. 39.74 − 9 =
  40. 40.229 − 99 =

Answer key

  1. 62
  2. 74
  3. 871
  4. 8
  5. 74
  6. 68
  7. 128
  8. 73
  9. 40
  10. 5
  11. 40
  12. 101
  13. 66
  14. 38
  15. 62
  16. 44
  17. 689
  18. 31
  19. 34
  20. 54
  21. 11
  22. 69
  23. 713
  24. 741
  25. 41
  26. 475
  27. 579
  28. 73
  29. 49
  30. 72
  31. 59
  32. 73
  33. 67
  34. 56
  35. 13
  36. 64
  37. 524
  38. 51
  39. 65
  40. 130

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