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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 531 · 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. 1.264 − 99 =
  2. 2.102 − 29 =
  3. 3.46 + 9 =
  4. 4.64 − 19 =
  5. 5.624 + 99 =
  6. 6.67 + 9 =
  7. 7.72 + 9 =
  8. 8.99 − 19 =
  9. 9.30 + 29 =
  10. 10.38 + 9 =
  11. 11.42 − 29 =
  12. 12.372 + 99 =
  13. 13.276 − 99 =
  14. 14.854 − 99 =
  15. 15.47 + 9 =
  16. 16.437 + 99 =
  17. 17.205 + 99 =
  18. 18.70 − 29 =
  19. 19.38 + 29 =
  20. 20.68 − 9 =
  21. 21.534 − 99 =
  22. 22.348 − 99 =
  23. 23.50 + 9 =
  24. 24.521 − 99 =
  25. 25.299 − 99 =
  26. 26.41 + 19 =
  27. 27.63 + 9 =
  28. 28.22 + 9 =
  29. 29.45 − 19 =
  30. 30.65 − 19 =
  31. 31.398 − 99 =
  32. 32.682 + 99 =
  33. 33.414 − 99 =
  34. 34.71 + 9 =
  35. 35.412 − 99 =
  36. 36.40 + 9 =
  37. 37.38 + 19 =
  38. 38.73 − 9 =
  39. 39.42 + 9 =
  40. 40.31 − 19 =

Answer key

  1. 165
  2. 73
  3. 55
  4. 45
  5. 723
  6. 76
  7. 81
  8. 80
  9. 59
  10. 47
  11. 13
  12. 471
  13. 177
  14. 755
  15. 56
  16. 536
  17. 304
  18. 41
  19. 67
  20. 59
  21. 435
  22. 249
  23. 59
  24. 422
  25. 200
  26. 60
  27. 72
  28. 31
  29. 26
  30. 46
  31. 299
  32. 781
  33. 315
  34. 80
  35. 313
  36. 49
  37. 57
  38. 64
  39. 51
  40. 12

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