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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 132 · 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. 2.602 − 99 =
  3. 3.233 − 99 =
  4. 4.57 + 9 =
  5. 5.191 + 99 =
  6. 6.542 − 99 =
  7. 7.73 + 9 =
  8. 8.37 + 9 =
  9. 9.36 + 19 =
  10. 10.74 − 29 =
  11. 11.88 − 19 =
  12. 12.505 − 99 =
  13. 13.96 − 19 =
  14. 14.71 + 29 =
  15. 15.60 − 29 =
  16. 16.63 − 9 =
  17. 17.77 − 29 =
  18. 18.290 + 99 =
  19. 19.64 + 29 =
  20. 20.47 + 19 =
  21. 21.34 − 9 =
  22. 22.123 + 99 =
  23. 23.290 − 99 =
  24. 24.797 − 99 =
  25. 25.31 + 9 =
  26. 26.42 + 9 =
  27. 27.326 + 99 =
  28. 28.52 − 29 =
  29. 29.375 + 99 =
  30. 30.67 + 9 =
  31. 31.26 + 29 =
  32. 32.215 + 99 =
  33. 33.39 − 29 =
  34. 34.28 + 19 =
  35. 35.41 + 19 =
  36. 36.73 + 29 =
  37. 37.28 + 9 =
  38. 38.77 + 19 =
  39. 39.82 − 19 =
  40. 40.60 − 19 =

Answer key

  1. 48
  2. 503
  3. 134
  4. 66
  5. 290
  6. 443
  7. 82
  8. 46
  9. 55
  10. 45
  11. 69
  12. 406
  13. 77
  14. 100
  15. 31
  16. 54
  17. 48
  18. 389
  19. 93
  20. 66
  21. 25
  22. 222
  23. 191
  24. 698
  25. 40
  26. 51
  27. 425
  28. 23
  29. 474
  30. 76
  31. 55
  32. 314
  33. 10
  34. 47
  35. 60
  36. 102
  37. 37
  38. 96
  39. 63
  40. 41

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