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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 966 · 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. 1.16 + 9 =
  2. 2.66 + 9 =
  3. 3.58 + 29 =
  4. 4.33 + 29 =
  5. 5.15 + 9 =
  6. 6.656 + 99 =
  7. 7.49 + 9 =
  8. 8.201 − 99 =
  9. 9.84 − 19 =
  10. 10.103 − 29 =
  11. 11.60 + 9 =
  12. 12.698 + 99 =
  13. 13.108 − 29 =
  14. 14.30 − 9 =
  15. 15.226 + 99 =
  16. 16.392 − 99 =
  17. 17.53 + 29 =
  18. 18.60 − 19 =
  19. 19.41 − 9 =
  20. 20.17 + 9 =
  21. 21.86 − 9 =
  22. 22.56 + 19 =
  23. 23.92 − 29 =
  24. 24.77 + 29 =
  25. 25.40 − 19 =
  26. 26.48 + 9 =
  27. 27.262 + 99 =
  28. 28.65 + 19 =
  29. 29.44 − 29 =
  30. 30.296 + 99 =
  31. 31.76 − 9 =
  32. 32.13 − 9 =
  33. 33.44 − 9 =
  34. 34.28 + 19 =
  35. 35.14 + 19 =
  36. 36.38 − 9 =
  37. 37.24 + 19 =
  38. 38.74 − 29 =
  39. 39.72 + 19 =
  40. 40.77 − 29 =

Answer key

  1. 25
  2. 75
  3. 87
  4. 62
  5. 24
  6. 755
  7. 58
  8. 102
  9. 65
  10. 74
  11. 69
  12. 797
  13. 79
  14. 21
  15. 325
  16. 293
  17. 82
  18. 41
  19. 32
  20. 26
  21. 77
  22. 75
  23. 63
  24. 106
  25. 21
  26. 57
  27. 361
  28. 84
  29. 15
  30. 395
  31. 67
  32. 4
  33. 35
  34. 47
  35. 33
  36. 29
  37. 43
  38. 45
  39. 91
  40. 48

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