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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 169 · 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. 1.54 + 29 =
  2. 2.41 − 9 =
  3. 3.35 + 9 =
  4. 4.64 − 9 =
  5. 5.600 + 99 =
  6. 6.57 + 19 =
  7. 7.67 + 9 =
  8. 8.709 + 99 =
  9. 9.60 − 19 =
  10. 10.102 − 29 =
  11. 11.94 − 19 =
  12. 12.79 − 9 =
  13. 13.15 + 29 =
  14. 14.349 − 99 =
  15. 15.572 + 99 =
  16. 16.36 − 19 =
  17. 17.54 + 19 =
  18. 18.28 + 19 =
  19. 19.792 + 99 =
  20. 20.208 + 99 =
  21. 21.48 + 9 =
  22. 22.73 + 19 =
  23. 23.74 − 9 =
  24. 24.201 − 99 =
  25. 25.46 + 9 =
  26. 26.257 − 99 =
  27. 27.60 + 19 =
  28. 28.99 − 29 =
  29. 29.26 + 19 =
  30. 30.760 − 99 =
  31. 31.41 + 19 =
  32. 32.39 + 9 =
  33. 33.89 − 29 =
  34. 34.37 + 9 =
  35. 35.670 − 99 =
  36. 36.25 + 19 =
  37. 37.101 − 29 =
  38. 38.64 − 19 =
  39. 39.34 + 9 =
  40. 40.78 + 19 =

Answer key

  1. 83
  2. 32
  3. 44
  4. 55
  5. 699
  6. 76
  7. 76
  8. 808
  9. 41
  10. 73
  11. 75
  12. 70
  13. 44
  14. 250
  15. 671
  16. 17
  17. 73
  18. 47
  19. 891
  20. 307
  21. 57
  22. 92
  23. 65
  24. 102
  25. 55
  26. 158
  27. 79
  28. 70
  29. 45
  30. 661
  31. 60
  32. 48
  33. 60
  34. 46
  35. 571
  36. 44
  37. 72
  38. 45
  39. 43
  40. 97

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