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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 659 · 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. 1.631 + 99 =
  2. 2.171 + 99 =
  3. 3.60 + 19 =
  4. 4.103 − 29 =
  5. 5.54 − 29 =
  6. 6.16 + 19 =
  7. 7.30 − 9 =
  8. 8.51 − 19 =
  9. 9.37 − 19 =
  10. 10.55 + 29 =
  11. 11.522 − 99 =
  12. 12.38 + 29 =
  13. 13.56 − 19 =
  14. 14.84 − 19 =
  15. 15.26 − 19 =
  16. 16.404 − 99 =
  17. 17.51 + 19 =
  18. 18.542 − 99 =
  19. 19.59 + 9 =
  20. 20.68 − 9 =
  21. 21.61 + 29 =
  22. 22.28 − 9 =
  23. 23.70 − 9 =
  24. 24.31 + 9 =
  25. 25.649 − 99 =
  26. 26.569 − 99 =
  27. 27.43 − 19 =
  28. 28.709 − 99 =
  29. 29.106 − 29 =
  30. 30.92 − 19 =
  31. 31.95 − 29 =
  32. 32.682 − 99 =
  33. 33.41 − 29 =
  34. 34.82 − 9 =
  35. 35.100 − 29 =
  36. 36.39 − 29 =
  37. 37.735 − 99 =
  38. 38.80 + 29 =
  39. 39.72 + 29 =
  40. 40.41 − 9 =

Answer key

  1. 730
  2. 270
  3. 79
  4. 74
  5. 25
  6. 35
  7. 21
  8. 32
  9. 18
  10. 84
  11. 423
  12. 67
  13. 37
  14. 65
  15. 7
  16. 305
  17. 70
  18. 443
  19. 68
  20. 59
  21. 90
  22. 19
  23. 61
  24. 40
  25. 550
  26. 470
  27. 24
  28. 610
  29. 77
  30. 73
  31. 66
  32. 583
  33. 12
  34. 73
  35. 71
  36. 10
  37. 636
  38. 109
  39. 101
  40. 32

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