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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 850 · 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. 1.50 + 9 =
  2. 2.24 − 9 =
  3. 3.53 + 9 =
  4. 4.59 + 19 =
  5. 5.86 − 19 =
  6. 6.14 + 29 =
  7. 7.50 − 9 =
  8. 8.75 − 19 =
  9. 9.287 − 99 =
  10. 10.54 + 9 =
  11. 11.75 − 9 =
  12. 12.33 − 29 =
  13. 13.95 − 19 =
  14. 14.399 − 99 =
  15. 15.560 + 99 =
  16. 16.789 + 99 =
  17. 17.407 − 99 =
  18. 18.37 + 9 =
  19. 19.106 − 29 =
  20. 20.100 − 29 =
  21. 21.38 + 29 =
  22. 22.243 + 99 =
  23. 23.52 − 9 =
  24. 24.65 + 19 =
  25. 25.18 + 19 =
  26. 26.60 + 29 =
  27. 27.77 + 9 =
  28. 28.61 − 29 =
  29. 29.86 − 29 =
  30. 30.15 − 9 =
  31. 31.455 + 99 =
  32. 32.74 − 19 =
  33. 33.59 − 29 =
  34. 34.32 − 19 =
  35. 35.518 − 99 =
  36. 36.26 + 9 =
  37. 37.14 + 9 =
  38. 38.33 + 19 =
  39. 39.566 + 99 =
  40. 40.81 − 9 =

Answer key

  1. 59
  2. 15
  3. 62
  4. 78
  5. 67
  6. 43
  7. 41
  8. 56
  9. 188
  10. 63
  11. 66
  12. 4
  13. 76
  14. 300
  15. 659
  16. 888
  17. 308
  18. 46
  19. 77
  20. 71
  21. 67
  22. 342
  23. 43
  24. 84
  25. 37
  26. 89
  27. 86
  28. 32
  29. 57
  30. 6
  31. 554
  32. 55
  33. 30
  34. 13
  35. 419
  36. 35
  37. 23
  38. 52
  39. 665
  40. 72

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