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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 981 · 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. 1.32 + 19 =
  2. 2.25 + 9 =
  3. 3.888 − 99 =
  4. 4.59 + 29 =
  5. 5.71 + 19 =
  6. 6.357 − 99 =
  7. 7.29 + 29 =
  8. 8.54 − 29 =
  9. 9.81 − 9 =
  10. 10.42 − 29 =
  11. 11.76 + 19 =
  12. 12.62 − 19 =
  13. 13.74 − 19 =
  14. 14.72 + 29 =
  15. 15.23 + 9 =
  16. 16.412 − 99 =
  17. 17.41 − 19 =
  18. 18.279 + 99 =
  19. 19.44 − 9 =
  20. 20.15 + 9 =
  21. 21.587 + 99 =
  22. 22.850 − 99 =
  23. 23.38 + 29 =
  24. 24.67 + 9 =
  25. 25.59 + 9 =
  26. 26.90 − 29 =
  27. 27.141 + 99 =
  28. 28.155 − 99 =
  29. 29.50 − 9 =
  30. 30.531 + 99 =
  31. 31.69 + 9 =
  32. 32.43 − 9 =
  33. 33.701 + 99 =
  34. 34.40 + 9 =
  35. 35.46 + 9 =
  36. 36.65 − 19 =
  37. 37.730 + 99 =
  38. 38.22 + 9 =
  39. 39.52 + 9 =
  40. 40.222 + 99 =

Answer key

  1. 51
  2. 34
  3. 789
  4. 88
  5. 90
  6. 258
  7. 58
  8. 25
  9. 72
  10. 13
  11. 95
  12. 43
  13. 55
  14. 101
  15. 32
  16. 313
  17. 22
  18. 378
  19. 35
  20. 24
  21. 686
  22. 751
  23. 67
  24. 76
  25. 68
  26. 61
  27. 240
  28. 56
  29. 41
  30. 630
  31. 78
  32. 34
  33. 800
  34. 49
  35. 55
  36. 46
  37. 829
  38. 31
  39. 61
  40. 321

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