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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 173 · 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. 1.151 − 99 =
  2. 2.15 − 9 =
  3. 3.82 − 19 =
  4. 4.55 + 19 =
  5. 5.35 + 29 =
  6. 6.87 − 19 =
  7. 7.53 + 29 =
  8. 8.653 − 99 =
  9. 9.77 + 19 =
  10. 10.49 − 29 =
  11. 11.334 + 99 =
  12. 12.56 − 9 =
  13. 13.59 + 29 =
  14. 14.44 + 29 =
  15. 15.25 + 29 =
  16. 16.706 − 99 =
  17. 17.34 − 19 =
  18. 18.13 + 19 =
  19. 19.56 + 29 =
  20. 20.17 − 9 =
  21. 21.87 − 9 =
  22. 22.53 + 9 =
  23. 23.79 + 19 =
  24. 24.18 − 9 =
  25. 25.38 + 9 =
  26. 26.29 + 19 =
  27. 27.28 + 9 =
  28. 28.60 − 29 =
  29. 29.92 − 29 =
  30. 30.102 − 29 =
  31. 31.68 + 9 =
  32. 32.56 − 29 =
  33. 33.22 + 9 =
  34. 34.323 − 99 =
  35. 35.36 − 29 =
  36. 36.15 + 29 =
  37. 37.38 + 19 =
  38. 38.21 + 19 =
  39. 39.730 + 99 =
  40. 40.98 − 29 =

Answer key

  1. 52
  2. 6
  3. 63
  4. 74
  5. 64
  6. 68
  7. 82
  8. 554
  9. 96
  10. 20
  11. 433
  12. 47
  13. 88
  14. 73
  15. 54
  16. 607
  17. 15
  18. 32
  19. 85
  20. 8
  21. 78
  22. 62
  23. 98
  24. 9
  25. 47
  26. 48
  27. 37
  28. 31
  29. 63
  30. 73
  31. 77
  32. 27
  33. 31
  34. 224
  35. 7
  36. 44
  37. 57
  38. 40
  39. 829
  40. 69

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