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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 902 · 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. 1.42 + 19 =
  2. 2.464 + 99 =
  3. 3.51 + 29 =
  4. 4.22 − 19 =
  5. 5.31 + 29 =
  6. 6.53 − 29 =
  7. 7.54 + 29 =
  8. 8.37 + 19 =
  9. 9.36 + 29 =
  10. 10.23 + 9 =
  11. 11.34 − 9 =
  12. 12.45 − 29 =
  13. 13.89 − 9 =
  14. 14.57 + 9 =
  15. 15.65 + 19 =
  16. 16.823 − 99 =
  17. 17.511 − 99 =
  18. 18.19 + 29 =
  19. 19.62 − 9 =
  20. 20.56 − 9 =
  21. 21.30 + 19 =
  22. 22.28 − 19 =
  23. 23.162 + 99 =
  24. 24.527 − 99 =
  25. 25.14 + 9 =
  26. 26.275 − 99 =
  27. 27.67 − 9 =
  28. 28.55 + 9 =
  29. 29.13 + 29 =
  30. 30.22 + 9 =
  31. 31.98 − 29 =
  32. 32.91 − 29 =
  33. 33.18 + 19 =
  34. 34.73 + 9 =
  35. 35.91 − 19 =
  36. 36.15 + 19 =
  37. 37.97 − 19 =
  38. 38.251 + 99 =
  39. 39.442 − 99 =
  40. 40.56 + 29 =

Answer key

  1. 61
  2. 563
  3. 80
  4. 3
  5. 60
  6. 24
  7. 83
  8. 56
  9. 65
  10. 32
  11. 25
  12. 16
  13. 80
  14. 66
  15. 84
  16. 724
  17. 412
  18. 48
  19. 53
  20. 47
  21. 49
  22. 9
  23. 261
  24. 428
  25. 23
  26. 176
  27. 58
  28. 64
  29. 42
  30. 31
  31. 69
  32. 62
  33. 37
  34. 82
  35. 72
  36. 34
  37. 78
  38. 350
  39. 343
  40. 85

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