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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 311 · 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. 1.634 − 99 =
  2. 2.880 − 99 =
  3. 3.43 − 9 =
  4. 4.498 + 99 =
  5. 5.50 − 29 =
  6. 6.65 + 9 =
  7. 7.54 + 9 =
  8. 8.48 − 19 =
  9. 9.63 − 9 =
  10. 10.45 + 19 =
  11. 11.300 + 99 =
  12. 12.27 + 19 =
  13. 13.12 + 19 =
  14. 14.83 − 9 =
  15. 15.163 − 99 =
  16. 16.55 − 9 =
  17. 17.31 + 9 =
  18. 18.398 − 99 =
  19. 19.51 − 19 =
  20. 20.22 − 19 =
  21. 21.25 − 19 =
  22. 22.44 + 29 =
  23. 23.76 + 9 =
  24. 24.72 + 19 =
  25. 25.70 − 19 =
  26. 26.14 − 9 =
  27. 27.46 + 29 =
  28. 28.37 − 19 =
  29. 29.709 − 99 =
  30. 30.18 + 19 =
  31. 31.143 + 99 =
  32. 32.378 + 99 =
  33. 33.715 − 99 =
  34. 34.32 + 29 =
  35. 35.476 + 99 =
  36. 36.35 + 9 =
  37. 37.232 + 99 =
  38. 38.71 − 19 =
  39. 39.38 + 29 =
  40. 40.61 + 9 =

Answer key

  1. 535
  2. 781
  3. 34
  4. 597
  5. 21
  6. 74
  7. 63
  8. 29
  9. 54
  10. 64
  11. 399
  12. 46
  13. 31
  14. 74
  15. 64
  16. 46
  17. 40
  18. 299
  19. 32
  20. 3
  21. 6
  22. 73
  23. 85
  24. 91
  25. 51
  26. 5
  27. 75
  28. 18
  29. 610
  30. 37
  31. 242
  32. 477
  33. 616
  34. 61
  35. 575
  36. 44
  37. 331
  38. 52
  39. 67
  40. 70

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