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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 515 · 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. 1.23 + 29 =
  2. 2.58 + 29 =
  3. 3.21 + 9 =
  4. 4.417 + 99 =
  5. 5.53 + 9 =
  6. 6.58 − 19 =
  7. 7.18 + 19 =
  8. 8.195 + 99 =
  9. 9.76 − 9 =
  10. 10.75 − 29 =
  11. 11.28 − 19 =
  12. 12.13 − 9 =
  13. 13.56 − 9 =
  14. 14.80 + 29 =
  15. 15.44 + 29 =
  16. 16.79 − 9 =
  17. 17.22 + 29 =
  18. 18.77 − 9 =
  19. 19.16 + 29 =
  20. 20.31 + 29 =
  21. 21.49 − 9 =
  22. 22.44 − 29 =
  23. 23.69 − 19 =
  24. 24.49 + 29 =
  25. 25.28 + 9 =
  26. 26.282 + 99 =
  27. 27.18 + 9 =
  28. 28.34 − 19 =
  29. 29.60 + 9 =
  30. 30.569 + 99 =
  31. 31.14 + 29 =
  32. 32.68 − 29 =
  33. 33.873 − 99 =
  34. 34.25 + 9 =
  35. 35.15 + 29 =
  36. 36.87 − 9 =
  37. 37.676 + 99 =
  38. 38.544 − 99 =
  39. 39.107 − 29 =
  40. 40.617 + 99 =

Answer key

  1. 52
  2. 87
  3. 30
  4. 516
  5. 62
  6. 39
  7. 37
  8. 294
  9. 67
  10. 46
  11. 9
  12. 4
  13. 47
  14. 109
  15. 73
  16. 70
  17. 51
  18. 68
  19. 45
  20. 60
  21. 40
  22. 15
  23. 50
  24. 78
  25. 37
  26. 381
  27. 27
  28. 15
  29. 69
  30. 668
  31. 43
  32. 39
  33. 774
  34. 34
  35. 44
  36. 78
  37. 775
  38. 445
  39. 78
  40. 716

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