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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 307 · 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. 1.29 + 19 =
  2. 2.22 + 29 =
  3. 3.52 + 9 =
  4. 4.23 − 19 =
  5. 5.47 + 29 =
  6. 6.43 + 19 =
  7. 7.196 + 99 =
  8. 8.48 + 29 =
  9. 9.356 + 99 =
  10. 10.70 + 29 =
  11. 11.19 + 9 =
  12. 12.21 − 9 =
  13. 13.14 + 29 =
  14. 14.75 + 29 =
  15. 15.60 − 19 =
  16. 16.669 + 99 =
  17. 17.56 + 9 =
  18. 18.72 + 29 =
  19. 19.33 − 9 =
  20. 20.38 + 19 =
  21. 21.18 + 29 =
  22. 22.15 − 9 =
  23. 23.735 − 99 =
  24. 24.49 + 9 =
  25. 25.83 − 19 =
  26. 26.649 − 99 =
  27. 27.75 + 9 =
  28. 28.78 + 19 =
  29. 29.13 − 9 =
  30. 30.66 + 9 =
  31. 31.78 − 9 =
  32. 32.26 + 19 =
  33. 33.23 + 19 =
  34. 34.351 − 99 =
  35. 35.70 − 19 =
  36. 36.14 − 9 =
  37. 37.86 − 29 =
  38. 38.535 − 99 =
  39. 39.786 + 99 =
  40. 40.68 − 29 =

Answer key

  1. 48
  2. 51
  3. 61
  4. 4
  5. 76
  6. 62
  7. 295
  8. 77
  9. 455
  10. 99
  11. 28
  12. 12
  13. 43
  14. 104
  15. 41
  16. 768
  17. 65
  18. 101
  19. 24
  20. 57
  21. 47
  22. 6
  23. 636
  24. 58
  25. 64
  26. 550
  27. 84
  28. 97
  29. 4
  30. 75
  31. 69
  32. 45
  33. 42
  34. 252
  35. 51
  36. 5
  37. 57
  38. 436
  39. 885
  40. 39

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