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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 297 · 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. 1.65 + 9 =
  2. 2.646 + 99 =
  3. 3.213 + 99 =
  4. 4.76 − 19 =
  5. 5.90 − 19 =
  6. 6.24 + 19 =
  7. 7.26 + 19 =
  8. 8.45 + 29 =
  9. 9.87 − 29 =
  10. 10.30 + 29 =
  11. 11.70 + 19 =
  12. 12.58 + 19 =
  13. 13.27 + 9 =
  14. 14.19 + 29 =
  15. 15.73 − 19 =
  16. 16.64 − 29 =
  17. 17.38 − 19 =
  18. 18.29 + 9 =
  19. 19.17 + 19 =
  20. 20.28 + 19 =
  21. 21.71 + 19 =
  22. 22.422 − 99 =
  23. 23.69 − 9 =
  24. 24.89 − 9 =
  25. 25.334 − 99 =
  26. 26.687 + 99 =
  27. 27.25 − 19 =
  28. 28.30 + 19 =
  29. 29.736 − 99 =
  30. 30.65 + 29 =
  31. 31.621 + 99 =
  32. 32.750 − 99 =
  33. 33.78 + 29 =
  34. 34.76 + 9 =
  35. 35.56 + 9 =
  36. 36.31 + 9 =
  37. 37.849 − 99 =
  38. 38.54 + 29 =
  39. 39.76 + 19 =
  40. 40.59 − 9 =

Answer key

  1. 74
  2. 745
  3. 312
  4. 57
  5. 71
  6. 43
  7. 45
  8. 74
  9. 58
  10. 59
  11. 89
  12. 77
  13. 36
  14. 48
  15. 54
  16. 35
  17. 19
  18. 38
  19. 36
  20. 47
  21. 90
  22. 323
  23. 60
  24. 80
  25. 235
  26. 786
  27. 6
  28. 49
  29. 637
  30. 94
  31. 720
  32. 651
  33. 107
  34. 85
  35. 65
  36. 40
  37. 750
  38. 83
  39. 95
  40. 50

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