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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 588 · 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. 1.40 + 29 =
  2. 2.49 − 9 =
  3. 3.69 + 9 =
  4. 4.67 − 9 =
  5. 5.230 + 99 =
  6. 6.65 − 19 =
  7. 7.24 + 9 =
  8. 8.613 + 99 =
  9. 9.15 + 9 =
  10. 10.388 − 99 =
  11. 11.68 + 19 =
  12. 12.55 + 9 =
  13. 13.34 + 29 =
  14. 14.121 + 99 =
  15. 15.44 − 29 =
  16. 16.66 + 19 =
  17. 17.74 + 29 =
  18. 18.76 − 9 =
  19. 19.82 − 19 =
  20. 20.50 − 29 =
  21. 21.33 + 19 =
  22. 22.34 + 19 =
  23. 23.30 + 19 =
  24. 24.29 + 29 =
  25. 25.22 + 9 =
  26. 26.54 − 9 =
  27. 27.64 + 19 =
  28. 28.39 + 29 =
  29. 29.63 − 29 =
  30. 30.22 − 9 =
  31. 31.237 − 99 =
  32. 32.30 − 9 =
  33. 33.72 − 19 =
  34. 34.42 + 19 =
  35. 35.668 + 99 =
  36. 36.51 − 9 =
  37. 37.421 + 99 =
  38. 38.165 + 99 =
  39. 39.56 + 9 =
  40. 40.73 − 29 =

Answer key

  1. 69
  2. 40
  3. 78
  4. 58
  5. 329
  6. 46
  7. 33
  8. 712
  9. 24
  10. 289
  11. 87
  12. 64
  13. 63
  14. 220
  15. 15
  16. 85
  17. 103
  18. 67
  19. 63
  20. 21
  21. 52
  22. 53
  23. 49
  24. 58
  25. 31
  26. 45
  27. 83
  28. 68
  29. 34
  30. 13
  31. 138
  32. 21
  33. 53
  34. 61
  35. 767
  36. 42
  37. 520
  38. 264
  39. 65
  40. 44

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