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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 290 · 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. 1.22 + 9 =
  2. 2.84 − 19 =
  3. 3.95 − 19 =
  4. 4.176 − 99 =
  5. 5.51 + 29 =
  6. 6.66 + 9 =
  7. 7.798 + 99 =
  8. 8.59 + 29 =
  9. 9.32 + 29 =
  10. 10.17 + 19 =
  11. 11.185 − 99 =
  12. 12.55 + 9 =
  13. 13.52 − 29 =
  14. 14.76 − 9 =
  15. 15.64 + 29 =
  16. 16.41 + 29 =
  17. 17.26 − 9 =
  18. 18.650 + 99 =
  19. 19.80 − 19 =
  20. 20.29 − 19 =
  21. 21.76 + 19 =
  22. 22.71 − 9 =
  23. 23.50 − 9 =
  24. 24.21 + 9 =
  25. 25.99 − 19 =
  26. 26.283 + 99 =
  27. 27.377 − 99 =
  28. 28.52 + 19 =
  29. 29.44 − 19 =
  30. 30.53 + 9 =
  31. 31.20 + 29 =
  32. 32.62 + 9 =
  33. 33.29 + 9 =
  34. 34.54 + 29 =
  35. 35.93 − 29 =
  36. 36.748 + 99 =
  37. 37.32 − 29 =
  38. 38.66 + 29 =
  39. 39.35 + 9 =
  40. 40.44 + 29 =

Answer key

  1. 31
  2. 65
  3. 76
  4. 77
  5. 80
  6. 75
  7. 897
  8. 88
  9. 61
  10. 36
  11. 86
  12. 64
  13. 23
  14. 67
  15. 93
  16. 70
  17. 17
  18. 749
  19. 61
  20. 10
  21. 95
  22. 62
  23. 41
  24. 30
  25. 80
  26. 382
  27. 278
  28. 71
  29. 25
  30. 62
  31. 49
  32. 71
  33. 38
  34. 83
  35. 64
  36. 847
  37. 3
  38. 95
  39. 44
  40. 73

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