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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 606 · 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. 1.48 + 19 =
  2. 2.69 + 19 =
  3. 3.59 + 29 =
  4. 4.29 + 9 =
  5. 5.106 − 29 =
  6. 6.37 − 19 =
  7. 7.62 + 29 =
  8. 8.18 + 9 =
  9. 9.75 + 19 =
  10. 10.200 + 99 =
  11. 11.48 − 19 =
  12. 12.79 + 9 =
  13. 13.12 + 9 =
  14. 14.45 − 9 =
  15. 15.149 + 99 =
  16. 16.46 − 19 =
  17. 17.412 − 99 =
  18. 18.83 − 9 =
  19. 19.32 − 9 =
  20. 20.73 − 9 =
  21. 21.619 − 99 =
  22. 22.47 − 29 =
  23. 23.237 − 99 =
  24. 24.438 + 99 =
  25. 25.75 + 9 =
  26. 26.254 − 99 =
  27. 27.21 + 29 =
  28. 28.24 − 19 =
  29. 29.18 − 9 =
  30. 30.61 + 29 =
  31. 31.85 − 9 =
  32. 32.27 − 9 =
  33. 33.39 − 19 =
  34. 34.16 + 19 =
  35. 35.58 − 29 =
  36. 36.57 − 19 =
  37. 37.74 − 9 =
  38. 38.49 − 29 =
  39. 39.29 + 29 =
  40. 40.894 − 99 =

Answer key

  1. 67
  2. 88
  3. 88
  4. 38
  5. 77
  6. 18
  7. 91
  8. 27
  9. 94
  10. 299
  11. 29
  12. 88
  13. 21
  14. 36
  15. 248
  16. 27
  17. 313
  18. 74
  19. 23
  20. 64
  21. 520
  22. 18
  23. 138
  24. 537
  25. 84
  26. 155
  27. 50
  28. 5
  29. 9
  30. 90
  31. 76
  32. 18
  33. 20
  34. 35
  35. 29
  36. 38
  37. 65
  38. 20
  39. 58
  40. 795

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