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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 617 · 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. 1.254 + 99 =
  2. 2.432 − 99 =
  3. 3.488 + 99 =
  4. 4.57 + 29 =
  5. 5.59 − 19 =
  6. 6.49 − 29 =
  7. 7.49 − 9 =
  8. 8.330 + 99 =
  9. 9.30 + 19 =
  10. 10.36 − 19 =
  11. 11.27 − 19 =
  12. 12.35 + 9 =
  13. 13.84 − 9 =
  14. 14.751 + 99 =
  15. 15.62 + 9 =
  16. 16.49 + 19 =
  17. 17.16 + 29 =
  18. 18.80 − 19 =
  19. 19.178 + 99 =
  20. 20.793 − 99 =
  21. 21.777 − 99 =
  22. 22.44 + 9 =
  23. 23.833 − 99 =
  24. 24.661 − 99 =
  25. 25.38 − 29 =
  26. 26.28 + 19 =
  27. 27.147 + 99 =
  28. 28.86 − 29 =
  29. 29.77 + 29 =
  30. 30.338 + 99 =
  31. 31.67 + 9 =
  32. 32.79 + 19 =
  33. 33.69 + 19 =
  34. 34.675 + 99 =
  35. 35.662 − 99 =
  36. 36.58 + 29 =
  37. 37.66 − 19 =
  38. 38.567 + 99 =
  39. 39.25 + 9 =
  40. 40.47 − 9 =

Answer key

  1. 353
  2. 333
  3. 587
  4. 86
  5. 40
  6. 20
  7. 40
  8. 429
  9. 49
  10. 17
  11. 8
  12. 44
  13. 75
  14. 850
  15. 71
  16. 68
  17. 45
  18. 61
  19. 277
  20. 694
  21. 678
  22. 53
  23. 734
  24. 562
  25. 9
  26. 47
  27. 246
  28. 57
  29. 106
  30. 437
  31. 76
  32. 98
  33. 88
  34. 774
  35. 563
  36. 87
  37. 47
  38. 666
  39. 34
  40. 38

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