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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 155 · 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. 1.210 + 99 =
  2. 2.96 − 19 =
  3. 3.56 − 29 =
  4. 4.91 − 29 =
  5. 5.757 − 99 =
  6. 6.219 + 99 =
  7. 7.13 − 9 =
  8. 8.40 + 29 =
  9. 9.577 + 99 =
  10. 10.239 + 99 =
  11. 11.75 − 19 =
  12. 12.39 − 19 =
  13. 13.45 − 19 =
  14. 14.53 − 9 =
  15. 15.240 − 99 =
  16. 16.466 − 99 =
  17. 17.51 − 19 =
  18. 18.32 + 9 =
  19. 19.166 − 99 =
  20. 20.35 + 29 =
  21. 21.648 − 99 =
  22. 22.77 + 29 =
  23. 23.61 − 9 =
  24. 24.14 + 29 =
  25. 25.103 − 29 =
  26. 26.75 + 19 =
  27. 27.62 + 9 =
  28. 28.36 − 29 =
  29. 29.369 − 99 =
  30. 30.18 + 19 =
  31. 31.29 + 29 =
  32. 32.41 + 9 =
  33. 33.82 − 9 =
  34. 34.25 + 9 =
  35. 35.715 − 99 =
  36. 36.626 + 99 =
  37. 37.75 + 29 =
  38. 38.74 − 29 =
  39. 39.107 − 29 =
  40. 40.72 − 29 =

Answer key

  1. 309
  2. 77
  3. 27
  4. 62
  5. 658
  6. 318
  7. 4
  8. 69
  9. 676
  10. 338
  11. 56
  12. 20
  13. 26
  14. 44
  15. 141
  16. 367
  17. 32
  18. 41
  19. 67
  20. 64
  21. 549
  22. 106
  23. 52
  24. 43
  25. 74
  26. 94
  27. 71
  28. 7
  29. 270
  30. 37
  31. 58
  32. 50
  33. 73
  34. 34
  35. 616
  36. 725
  37. 104
  38. 45
  39. 78
  40. 43

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