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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 587 · 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. 1.98 − 19 =
  2. 2.314 − 99 =
  3. 3.277 − 99 =
  4. 4.818 − 99 =
  5. 5.155 − 99 =
  6. 6.783 − 99 =
  7. 7.36 + 29 =
  8. 8.51 + 29 =
  9. 9.46 + 29 =
  10. 10.160 + 99 =
  11. 11.56 − 9 =
  12. 12.526 + 99 =
  13. 13.22 − 9 =
  14. 14.648 + 99 =
  15. 15.37 + 19 =
  16. 16.639 + 99 =
  17. 17.14 + 29 =
  18. 18.38 − 19 =
  19. 19.96 − 29 =
  20. 20.29 + 19 =
  21. 21.85 − 29 =
  22. 22.76 + 29 =
  23. 23.42 + 29 =
  24. 24.53 + 19 =
  25. 25.20 + 29 =
  26. 26.649 + 99 =
  27. 27.417 − 99 =
  28. 28.22 + 19 =
  29. 29.83 − 9 =
  30. 30.71 + 9 =
  31. 31.72 + 9 =
  32. 32.52 + 9 =
  33. 33.79 + 29 =
  34. 34.64 + 9 =
  35. 35.18 + 29 =
  36. 36.78 + 9 =
  37. 37.229 + 99 =
  38. 38.343 + 99 =
  39. 39.63 + 19 =
  40. 40.44 + 19 =

Answer key

  1. 79
  2. 215
  3. 178
  4. 719
  5. 56
  6. 684
  7. 65
  8. 80
  9. 75
  10. 259
  11. 47
  12. 625
  13. 13
  14. 747
  15. 56
  16. 738
  17. 43
  18. 19
  19. 67
  20. 48
  21. 56
  22. 105
  23. 71
  24. 72
  25. 49
  26. 748
  27. 318
  28. 41
  29. 74
  30. 80
  31. 81
  32. 61
  33. 108
  34. 73
  35. 47
  36. 87
  37. 328
  38. 442
  39. 82
  40. 63

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