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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 681 · 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. 1.220 + 99 =
  2. 2.92 − 19 =
  3. 3.30 + 19 =
  4. 4.87 − 29 =
  5. 5.20 + 9 =
  6. 6.54 + 9 =
  7. 7.417 − 99 =
  8. 8.226 + 99 =
  9. 9.24 − 9 =
  10. 10.73 + 9 =
  11. 11.71 + 29 =
  12. 12.28 − 9 =
  13. 13.98 − 29 =
  14. 14.76 − 19 =
  15. 15.30 + 29 =
  16. 16.32 − 19 =
  17. 17.16 − 9 =
  18. 18.64 − 9 =
  19. 19.22 − 9 =
  20. 20.49 − 19 =
  21. 21.58 + 9 =
  22. 22.863 − 99 =
  23. 23.55 + 29 =
  24. 24.497 − 99 =
  25. 25.35 + 29 =
  26. 26.40 − 29 =
  27. 27.46 + 19 =
  28. 28.78 − 19 =
  29. 29.648 + 99 =
  30. 30.17 − 9 =
  31. 31.38 − 29 =
  32. 32.31 − 9 =
  33. 33.66 − 29 =
  34. 34.40 + 19 =
  35. 35.31 + 19 =
  36. 36.79 − 19 =
  37. 37.28 + 9 =
  38. 38.215 − 99 =
  39. 39.45 − 29 =
  40. 40.53 + 9 =

Answer key

  1. 319
  2. 73
  3. 49
  4. 58
  5. 29
  6. 63
  7. 318
  8. 325
  9. 15
  10. 82
  11. 100
  12. 19
  13. 69
  14. 57
  15. 59
  16. 13
  17. 7
  18. 55
  19. 13
  20. 30
  21. 67
  22. 764
  23. 84
  24. 398
  25. 64
  26. 11
  27. 65
  28. 59
  29. 747
  30. 8
  31. 9
  32. 22
  33. 37
  34. 59
  35. 50
  36. 60
  37. 37
  38. 116
  39. 16
  40. 62

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