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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 662 · 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. 1.72 − 9 =
  2. 2.250 − 99 =
  3. 3.53 + 9 =
  4. 4.319 − 99 =
  5. 5.69 + 19 =
  6. 6.61 − 29 =
  7. 7.80 + 29 =
  8. 8.31 + 19 =
  9. 9.63 + 19 =
  10. 10.54 + 9 =
  11. 11.22 + 19 =
  12. 12.44 + 29 =
  13. 13.54 − 9 =
  14. 14.357 + 99 =
  15. 15.456 − 99 =
  16. 16.30 + 29 =
  17. 17.38 − 9 =
  18. 18.97 − 19 =
  19. 19.22 + 29 =
  20. 20.37 + 9 =
  21. 21.28 + 19 =
  22. 22.66 + 19 =
  23. 23.24 + 29 =
  24. 24.748 − 99 =
  25. 25.27 + 9 =
  26. 26.45 + 9 =
  27. 27.233 + 99 =
  28. 28.42 + 9 =
  29. 29.60 + 19 =
  30. 30.23 + 29 =
  31. 31.44 − 19 =
  32. 32.67 − 9 =
  33. 33.677 + 99 =
  34. 34.40 − 19 =
  35. 35.340 − 99 =
  36. 36.57 + 9 =
  37. 37.24 + 9 =
  38. 38.39 + 19 =
  39. 39.22 + 9 =
  40. 40.44 − 9 =

Answer key

  1. 63
  2. 151
  3. 62
  4. 220
  5. 88
  6. 32
  7. 109
  8. 50
  9. 82
  10. 63
  11. 41
  12. 73
  13. 45
  14. 456
  15. 357
  16. 59
  17. 29
  18. 78
  19. 51
  20. 46
  21. 47
  22. 85
  23. 53
  24. 649
  25. 36
  26. 54
  27. 332
  28. 51
  29. 79
  30. 52
  31. 25
  32. 58
  33. 776
  34. 21
  35. 241
  36. 66
  37. 33
  38. 58
  39. 31
  40. 35

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