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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 519 · 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. 1.70 − 9 =
  2. 2.53 − 29 =
  3. 3.78 + 29 =
  4. 4.53 + 19 =
  5. 5.392 − 99 =
  6. 6.741 − 99 =
  7. 7.353 − 99 =
  8. 8.28 + 29 =
  9. 9.47 − 29 =
  10. 10.29 + 9 =
  11. 11.31 − 9 =
  12. 12.14 + 29 =
  13. 13.54 − 9 =
  14. 14.79 + 9 =
  15. 15.24 − 19 =
  16. 16.74 + 9 =
  17. 17.67 + 29 =
  18. 18.490 + 99 =
  19. 19.383 − 99 =
  20. 20.76 + 19 =
  21. 21.48 − 9 =
  22. 22.86 − 9 =
  23. 23.13 + 9 =
  24. 24.717 + 99 =
  25. 25.39 − 29 =
  26. 26.354 + 99 =
  27. 27.41 + 19 =
  28. 28.61 − 9 =
  29. 29.56 + 29 =
  30. 30.83 − 9 =
  31. 31.45 + 19 =
  32. 32.85 − 29 =
  33. 33.786 + 99 =
  34. 34.54 − 19 =
  35. 35.30 + 19 =
  36. 36.70 − 19 =
  37. 37.73 − 19 =
  38. 38.79 − 19 =
  39. 39.681 − 99 =
  40. 40.63 + 9 =

Answer key

  1. 61
  2. 24
  3. 107
  4. 72
  5. 293
  6. 642
  7. 254
  8. 57
  9. 18
  10. 38
  11. 22
  12. 43
  13. 45
  14. 88
  15. 5
  16. 83
  17. 96
  18. 589
  19. 284
  20. 95
  21. 39
  22. 77
  23. 22
  24. 816
  25. 10
  26. 453
  27. 60
  28. 52
  29. 85
  30. 74
  31. 64
  32. 56
  33. 885
  34. 35
  35. 49
  36. 51
  37. 54
  38. 60
  39. 582
  40. 72

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