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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 857 · 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. 1.42 + 19 =
  2. 2.310 + 99 =
  3. 3.78 + 9 =
  4. 4.804 − 99 =
  5. 5.24 + 29 =
  6. 6.518 − 99 =
  7. 7.636 + 99 =
  8. 8.70 + 9 =
  9. 9.94 − 29 =
  10. 10.386 + 99 =
  11. 11.833 − 99 =
  12. 12.400 − 99 =
  13. 13.26 + 29 =
  14. 14.34 − 9 =
  15. 15.17 − 9 =
  16. 16.25 − 19 =
  17. 17.239 + 99 =
  18. 18.33 − 9 =
  19. 19.209 + 99 =
  20. 20.58 − 19 =
  21. 21.168 + 99 =
  22. 22.38 − 9 =
  23. 23.37 + 9 =
  24. 24.568 − 99 =
  25. 25.408 + 99 =
  26. 26.69 + 9 =
  27. 27.466 + 99 =
  28. 28.75 + 9 =
  29. 29.64 + 19 =
  30. 30.77 − 9 =
  31. 31.32 − 19 =
  32. 32.35 − 9 =
  33. 33.753 + 99 =
  34. 34.40 − 9 =
  35. 35.38 − 29 =
  36. 36.214 + 99 =
  37. 37.66 + 19 =
  38. 38.39 + 29 =
  39. 39.429 − 99 =
  40. 40.61 − 19 =

Answer key

  1. 61
  2. 409
  3. 87
  4. 705
  5. 53
  6. 419
  7. 735
  8. 79
  9. 65
  10. 485
  11. 734
  12. 301
  13. 55
  14. 25
  15. 8
  16. 6
  17. 338
  18. 24
  19. 308
  20. 39
  21. 267
  22. 29
  23. 46
  24. 469
  25. 507
  26. 78
  27. 565
  28. 84
  29. 83
  30. 68
  31. 13
  32. 26
  33. 852
  34. 31
  35. 9
  36. 313
  37. 85
  38. 68
  39. 330
  40. 42

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