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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 388 · 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. 1.773 − 99 =
  2. 2.88 − 19 =
  3. 3.39 + 29 =
  4. 4.879 − 99 =
  5. 5.42 + 9 =
  6. 6.26 + 19 =
  7. 7.533 + 99 =
  8. 8.557 + 99 =
  9. 9.48 − 29 =
  10. 10.56 − 19 =
  11. 11.37 + 19 =
  12. 12.66 + 29 =
  13. 13.645 − 99 =
  14. 14.858 − 99 =
  15. 15.23 + 19 =
  16. 16.40 − 19 =
  17. 17.97 − 29 =
  18. 18.44 + 9 =
  19. 19.67 + 19 =
  20. 20.30 − 9 =
  21. 21.453 − 99 =
  22. 22.88 − 9 =
  23. 23.45 + 19 =
  24. 24.171 − 99 =
  25. 25.23 + 9 =
  26. 26.35 + 9 =
  27. 27.59 − 29 =
  28. 28.737 + 99 =
  29. 29.61 + 29 =
  30. 30.60 − 29 =
  31. 31.106 − 29 =
  32. 32.439 + 99 =
  33. 33.62 + 19 =
  34. 34.42 + 19 =
  35. 35.17 + 29 =
  36. 36.401 − 99 =
  37. 37.19 + 9 =
  38. 38.21 + 19 =
  39. 39.57 + 29 =
  40. 40.27 + 9 =

Answer key

  1. 674
  2. 69
  3. 68
  4. 780
  5. 51
  6. 45
  7. 632
  8. 656
  9. 19
  10. 37
  11. 56
  12. 95
  13. 546
  14. 759
  15. 42
  16. 21
  17. 68
  18. 53
  19. 86
  20. 21
  21. 354
  22. 79
  23. 64
  24. 72
  25. 32
  26. 44
  27. 30
  28. 836
  29. 90
  30. 31
  31. 77
  32. 538
  33. 81
  34. 61
  35. 46
  36. 302
  37. 28
  38. 40
  39. 86
  40. 36

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