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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 877 · 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. 1.608 + 99 =
  2. 2.399 + 99 =
  3. 3.76 − 29 =
  4. 4.86 − 9 =
  5. 5.381 + 99 =
  6. 6.65 + 9 =
  7. 7.132 + 99 =
  8. 8.47 − 9 =
  9. 9.37 − 9 =
  10. 10.50 + 19 =
  11. 11.79 − 9 =
  12. 12.78 − 19 =
  13. 13.64 − 9 =
  14. 14.730 + 99 =
  15. 15.79 − 19 =
  16. 16.228 + 99 =
  17. 17.73 − 9 =
  18. 18.74 + 9 =
  19. 19.43 − 29 =
  20. 20.49 − 19 =
  21. 21.70 + 9 =
  22. 22.66 − 29 =
  23. 23.54 + 9 =
  24. 24.34 − 19 =
  25. 25.17 + 19 =
  26. 26.104 − 29 =
  27. 27.24 + 19 =
  28. 28.107 − 29 =
  29. 29.604 − 99 =
  30. 30.77 − 19 =
  31. 31.40 + 9 =
  32. 32.191 + 99 =
  33. 33.54 + 19 =
  34. 34.78 − 29 =
  35. 35.28 − 19 =
  36. 36.631 + 99 =
  37. 37.68 − 9 =
  38. 38.26 − 9 =
  39. 39.81 − 19 =
  40. 40.26 − 19 =

Answer key

  1. 707
  2. 498
  3. 47
  4. 77
  5. 480
  6. 74
  7. 231
  8. 38
  9. 28
  10. 69
  11. 70
  12. 59
  13. 55
  14. 829
  15. 60
  16. 327
  17. 64
  18. 83
  19. 14
  20. 30
  21. 79
  22. 37
  23. 63
  24. 15
  25. 36
  26. 75
  27. 43
  28. 78
  29. 505
  30. 58
  31. 49
  32. 290
  33. 73
  34. 49
  35. 9
  36. 730
  37. 59
  38. 17
  39. 62
  40. 7

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