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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 945 · 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. 1.20 + 9 =
  2. 2.610 − 99 =
  3. 3.53 + 9 =
  4. 4.71 − 29 =
  5. 5.67 − 9 =
  6. 6.55 − 9 =
  7. 7.13 + 9 =
  8. 8.18 + 19 =
  9. 9.55 + 19 =
  10. 10.44 + 29 =
  11. 11.27 − 9 =
  12. 12.78 − 9 =
  13. 13.37 − 19 =
  14. 14.213 − 99 =
  15. 15.37 + 19 =
  16. 16.63 − 9 =
  17. 17.19 + 9 =
  18. 18.28 + 9 =
  19. 19.624 + 99 =
  20. 20.866 − 99 =
  21. 21.399 − 99 =
  22. 22.67 + 9 =
  23. 23.72 + 29 =
  24. 24.33 + 29 =
  25. 25.63 + 9 =
  26. 26.59 − 9 =
  27. 27.224 − 99 =
  28. 28.37 + 9 =
  29. 29.50 − 19 =
  30. 30.33 + 9 =
  31. 31.45 − 29 =
  32. 32.62 + 9 =
  33. 33.80 − 29 =
  34. 34.73 + 9 =
  35. 35.13 + 19 =
  36. 36.33 − 29 =
  37. 37.728 + 99 =
  38. 38.129 + 99 =
  39. 39.32 + 29 =
  40. 40.477 + 99 =

Answer key

  1. 29
  2. 511
  3. 62
  4. 42
  5. 58
  6. 46
  7. 22
  8. 37
  9. 74
  10. 73
  11. 18
  12. 69
  13. 18
  14. 114
  15. 56
  16. 54
  17. 28
  18. 37
  19. 723
  20. 767
  21. 300
  22. 76
  23. 101
  24. 62
  25. 72
  26. 50
  27. 125
  28. 46
  29. 31
  30. 42
  31. 16
  32. 71
  33. 51
  34. 82
  35. 32
  36. 4
  37. 827
  38. 228
  39. 61
  40. 576

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