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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 177 · 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. 1.420 − 99 =
  2. 2.47 + 29 =
  3. 3.400 − 99 =
  4. 4.68 − 19 =
  5. 5.28 + 19 =
  6. 6.25 + 9 =
  7. 7.523 + 99 =
  8. 8.80 − 29 =
  9. 9.209 + 99 =
  10. 10.398 + 99 =
  11. 11.25 − 9 =
  12. 12.72 + 19 =
  13. 13.34 + 9 =
  14. 14.18 + 9 =
  15. 15.17 + 9 =
  16. 16.52 − 29 =
  17. 17.71 − 9 =
  18. 18.77 − 9 =
  19. 19.70 + 19 =
  20. 20.20 + 29 =
  21. 21.590 − 99 =
  22. 22.30 + 9 =
  23. 23.828 − 99 =
  24. 24.749 + 99 =
  25. 25.80 + 9 =
  26. 26.50 + 9 =
  27. 27.105 − 29 =
  28. 28.14 + 29 =
  29. 29.51 + 19 =
  30. 30.88 − 9 =
  31. 31.732 + 99 =
  32. 32.93 − 29 =
  33. 33.181 − 99 =
  34. 34.15 + 9 =
  35. 35.605 − 99 =
  36. 36.53 + 19 =
  37. 37.42 + 9 =
  38. 38.51 − 9 =
  39. 39.81 − 9 =
  40. 40.75 − 9 =

Answer key

  1. 321
  2. 76
  3. 301
  4. 49
  5. 47
  6. 34
  7. 622
  8. 51
  9. 308
  10. 497
  11. 16
  12. 91
  13. 43
  14. 27
  15. 26
  16. 23
  17. 62
  18. 68
  19. 89
  20. 49
  21. 491
  22. 39
  23. 729
  24. 848
  25. 89
  26. 59
  27. 76
  28. 43
  29. 70
  30. 79
  31. 831
  32. 64
  33. 82
  34. 24
  35. 506
  36. 72
  37. 51
  38. 42
  39. 72
  40. 66

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