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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 610 · 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. 1.192 + 99 =
  2. 2.655 + 99 =
  3. 3.57 − 9 =
  4. 4.34 + 19 =
  5. 5.177 + 99 =
  6. 6.800 − 99 =
  7. 7.97 − 29 =
  8. 8.43 − 9 =
  9. 9.47 + 9 =
  10. 10.78 + 19 =
  11. 11.706 + 99 =
  12. 12.50 + 29 =
  13. 13.66 + 29 =
  14. 14.216 + 99 =
  15. 15.16 + 19 =
  16. 16.19 + 19 =
  17. 17.96 − 29 =
  18. 18.51 + 9 =
  19. 19.18 + 19 =
  20. 20.38 + 19 =
  21. 21.103 − 29 =
  22. 22.58 − 29 =
  23. 23.31 + 9 =
  24. 24.32 + 9 =
  25. 25.35 − 19 =
  26. 26.343 + 99 =
  27. 27.164 + 99 =
  28. 28.36 − 29 =
  29. 29.32 − 19 =
  30. 30.57 − 19 =
  31. 31.221 − 99 =
  32. 32.799 + 99 =
  33. 33.42 − 29 =
  34. 34.38 + 29 =
  35. 35.728 − 99 =
  36. 36.372 + 99 =
  37. 37.433 + 99 =
  38. 38.74 − 9 =
  39. 39.47 + 29 =
  40. 40.41 + 19 =

Answer key

  1. 291
  2. 754
  3. 48
  4. 53
  5. 276
  6. 701
  7. 68
  8. 34
  9. 56
  10. 97
  11. 805
  12. 79
  13. 95
  14. 315
  15. 35
  16. 38
  17. 67
  18. 60
  19. 37
  20. 57
  21. 74
  22. 29
  23. 40
  24. 41
  25. 16
  26. 442
  27. 263
  28. 7
  29. 13
  30. 38
  31. 122
  32. 898
  33. 13
  34. 67
  35. 629
  36. 471
  37. 532
  38. 65
  39. 76
  40. 60

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