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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 414 · 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. 1.63 + 19 =
  2. 2.50 + 9 =
  3. 3.20 + 29 =
  4. 4.65 + 29 =
  5. 5.107 − 29 =
  6. 6.352 − 99 =
  7. 7.29 + 19 =
  8. 8.676 − 99 =
  9. 9.46 + 9 =
  10. 10.67 − 29 =
  11. 11.197 + 99 =
  12. 12.94 − 29 =
  13. 13.617 − 99 =
  14. 14.38 + 9 =
  15. 15.26 + 9 =
  16. 16.53 + 19 =
  17. 17.92 − 29 =
  18. 18.39 − 9 =
  19. 19.84 − 29 =
  20. 20.234 + 99 =
  21. 21.83 − 9 =
  22. 22.91 − 29 =
  23. 23.66 − 29 =
  24. 24.59 − 9 =
  25. 25.39 − 19 =
  26. 26.233 − 99 =
  27. 27.36 + 19 =
  28. 28.595 + 99 =
  29. 29.357 + 99 =
  30. 30.707 + 99 =
  31. 31.88 − 9 =
  32. 32.18 + 19 =
  33. 33.31 − 19 =
  34. 34.25 + 19 =
  35. 35.70 + 9 =
  36. 36.475 + 99 =
  37. 37.37 + 29 =
  38. 38.12 + 19 =
  39. 39.30 − 9 =
  40. 40.59 + 9 =

Answer key

  1. 82
  2. 59
  3. 49
  4. 94
  5. 78
  6. 253
  7. 48
  8. 577
  9. 55
  10. 38
  11. 296
  12. 65
  13. 518
  14. 47
  15. 35
  16. 72
  17. 63
  18. 30
  19. 55
  20. 333
  21. 74
  22. 62
  23. 37
  24. 50
  25. 20
  26. 134
  27. 55
  28. 694
  29. 456
  30. 806
  31. 79
  32. 37
  33. 12
  34. 44
  35. 79
  36. 574
  37. 66
  38. 31
  39. 21
  40. 68

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