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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 537 · 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. 1.38 + 29 =
  2. 2.614 + 99 =
  3. 3.580 + 99 =
  4. 4.50 + 9 =
  5. 5.25 + 29 =
  6. 6.23 + 9 =
  7. 7.74 − 9 =
  8. 8.88 − 9 =
  9. 9.363 − 99 =
  10. 10.179 + 99 =
  11. 11.59 + 19 =
  12. 12.52 − 9 =
  13. 13.69 − 19 =
  14. 14.41 + 19 =
  15. 15.286 − 99 =
  16. 16.523 − 99 =
  17. 17.79 − 19 =
  18. 18.280 − 99 =
  19. 19.287 − 99 =
  20. 20.88 − 19 =
  21. 21.73 + 9 =
  22. 22.56 − 19 =
  23. 23.76 − 9 =
  24. 24.78 + 9 =
  25. 25.66 + 9 =
  26. 26.70 + 9 =
  27. 27.24 + 19 =
  28. 28.96 − 19 =
  29. 29.19 − 9 =
  30. 30.64 + 9 =
  31. 31.80 − 9 =
  32. 32.16 + 19 =
  33. 33.443 − 99 =
  34. 34.93 − 19 =
  35. 35.26 − 9 =
  36. 36.54 + 29 =
  37. 37.305 − 99 =
  38. 38.36 − 9 =
  39. 39.55 + 29 =
  40. 40.46 − 19 =

Answer key

  1. 67
  2. 713
  3. 679
  4. 59
  5. 54
  6. 32
  7. 65
  8. 79
  9. 264
  10. 278
  11. 78
  12. 43
  13. 50
  14. 60
  15. 187
  16. 424
  17. 60
  18. 181
  19. 188
  20. 69
  21. 82
  22. 37
  23. 67
  24. 87
  25. 75
  26. 79
  27. 43
  28. 77
  29. 10
  30. 73
  31. 71
  32. 35
  33. 344
  34. 74
  35. 17
  36. 83
  37. 206
  38. 27
  39. 84
  40. 27

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