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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 834 · 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. 1.442 − 99 =
  2. 2.433 + 99 =
  3. 3.93 − 19 =
  4. 4.78 + 9 =
  5. 5.52 + 19 =
  6. 6.27 − 9 =
  7. 7.78 + 29 =
  8. 8.749 + 99 =
  9. 9.69 − 19 =
  10. 10.646 − 99 =
  11. 11.60 + 9 =
  12. 12.33 + 9 =
  13. 13.61 − 19 =
  14. 14.54 − 19 =
  15. 15.40 + 9 =
  16. 16.34 + 29 =
  17. 17.546 + 99 =
  18. 18.37 − 9 =
  19. 19.24 − 19 =
  20. 20.32 − 9 =
  21. 21.33 − 29 =
  22. 22.83 − 29 =
  23. 23.50 + 19 =
  24. 24.382 − 99 =
  25. 25.655 − 99 =
  26. 26.52 − 9 =
  27. 27.77 + 9 =
  28. 28.79 + 19 =
  29. 29.88 − 19 =
  30. 30.14 + 19 =
  31. 31.495 + 99 =
  32. 32.24 + 19 =
  33. 33.62 + 29 =
  34. 34.30 + 9 =
  35. 35.22 + 29 =
  36. 36.45 + 19 =
  37. 37.34 + 19 =
  38. 38.79 + 29 =
  39. 39.68 − 19 =
  40. 40.391 + 99 =

Answer key

  1. 343
  2. 532
  3. 74
  4. 87
  5. 71
  6. 18
  7. 107
  8. 848
  9. 50
  10. 547
  11. 69
  12. 42
  13. 42
  14. 35
  15. 49
  16. 63
  17. 645
  18. 28
  19. 5
  20. 23
  21. 4
  22. 54
  23. 69
  24. 283
  25. 556
  26. 43
  27. 86
  28. 98
  29. 69
  30. 33
  31. 594
  32. 43
  33. 91
  34. 39
  35. 51
  36. 64
  37. 53
  38. 108
  39. 49
  40. 490

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