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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 912 · 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. 1.15 − 9 =
  2. 2.534 + 99 =
  3. 3.562 − 99 =
  4. 4.369 − 99 =
  5. 5.37 − 29 =
  6. 6.39 + 29 =
  7. 7.75 − 29 =
  8. 8.38 + 19 =
  9. 9.40 + 19 =
  10. 10.65 + 29 =
  11. 11.51 − 29 =
  12. 12.382 + 99 =
  13. 13.57 + 9 =
  14. 14.31 − 9 =
  15. 15.797 + 99 =
  16. 16.88 − 19 =
  17. 17.99 − 19 =
  18. 18.87 − 29 =
  19. 19.101 − 29 =
  20. 20.21 − 9 =
  21. 21.80 + 29 =
  22. 22.35 + 29 =
  23. 23.88 − 9 =
  24. 24.16 + 9 =
  25. 25.31 + 29 =
  26. 26.429 + 99 =
  27. 27.31 + 19 =
  28. 28.334 + 99 =
  29. 29.393 + 99 =
  30. 30.20 + 19 =
  31. 31.36 + 9 =
  32. 32.631 + 99 =
  33. 33.17 + 19 =
  34. 34.23 + 9 =
  35. 35.106 − 29 =
  36. 36.451 + 99 =
  37. 37.77 + 29 =
  38. 38.82 − 9 =
  39. 39.50 + 9 =
  40. 40.25 + 19 =

Answer key

  1. 6
  2. 633
  3. 463
  4. 270
  5. 8
  6. 68
  7. 46
  8. 57
  9. 59
  10. 94
  11. 22
  12. 481
  13. 66
  14. 22
  15. 896
  16. 69
  17. 80
  18. 58
  19. 72
  20. 12
  21. 109
  22. 64
  23. 79
  24. 25
  25. 60
  26. 528
  27. 50
  28. 433
  29. 492
  30. 39
  31. 45
  32. 730
  33. 36
  34. 32
  35. 77
  36. 550
  37. 106
  38. 73
  39. 59
  40. 44

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