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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 756 · 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. 1.68 − 19 =
  2. 2.40 − 29 =
  3. 3.31 + 29 =
  4. 4.220 + 99 =
  5. 5.72 − 9 =
  6. 6.774 + 99 =
  7. 7.134 + 99 =
  8. 8.54 − 9 =
  9. 9.30 − 9 =
  10. 10.87 − 9 =
  11. 11.57 + 29 =
  12. 12.22 − 9 =
  13. 13.19 − 9 =
  14. 14.26 + 19 =
  15. 15.633 + 99 =
  16. 16.88 − 9 =
  17. 17.899 − 99 =
  18. 18.491 − 99 =
  19. 19.210 − 99 =
  20. 20.74 − 19 =
  21. 21.282 − 99 =
  22. 22.33 − 19 =
  23. 23.51 + 29 =
  24. 24.766 + 99 =
  25. 25.68 + 29 =
  26. 26.722 − 99 =
  27. 27.66 + 9 =
  28. 28.76 + 19 =
  29. 29.77 − 19 =
  30. 30.42 − 29 =
  31. 31.13 + 9 =
  32. 32.58 + 9 =
  33. 33.33 + 29 =
  34. 34.23 − 19 =
  35. 35.20 + 9 =
  36. 36.44 + 29 =
  37. 37.17 + 19 =
  38. 38.441 + 99 =
  39. 39.32 + 9 =
  40. 40.200 − 99 =

Answer key

  1. 49
  2. 11
  3. 60
  4. 319
  5. 63
  6. 873
  7. 233
  8. 45
  9. 21
  10. 78
  11. 86
  12. 13
  13. 10
  14. 45
  15. 732
  16. 79
  17. 800
  18. 392
  19. 111
  20. 55
  21. 183
  22. 14
  23. 80
  24. 865
  25. 97
  26. 623
  27. 75
  28. 95
  29. 58
  30. 13
  31. 22
  32. 67
  33. 62
  34. 4
  35. 29
  36. 73
  37. 36
  38. 540
  39. 41
  40. 101

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