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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 650 · 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. 1.30 + 19 =
  2. 2.23 + 29 =
  3. 3.654 + 99 =
  4. 4.73 − 9 =
  5. 5.60 + 29 =
  6. 6.23 − 19 =
  7. 7.36 − 9 =
  8. 8.41 − 29 =
  9. 9.45 + 9 =
  10. 10.51 − 29 =
  11. 11.75 + 19 =
  12. 12.551 − 99 =
  13. 13.23 + 19 =
  14. 14.74 + 19 =
  15. 15.392 − 99 =
  16. 16.45 − 9 =
  17. 17.68 − 19 =
  18. 18.62 + 29 =
  19. 19.53 + 19 =
  20. 20.38 − 29 =
  21. 21.54 − 29 =
  22. 22.543 + 99 =
  23. 23.60 − 29 =
  24. 24.31 + 29 =
  25. 25.276 + 99 =
  26. 26.43 − 29 =
  27. 27.77 + 19 =
  28. 28.385 + 99 =
  29. 29.594 − 99 =
  30. 30.23 + 9 =
  31. 31.524 + 99 =
  32. 32.32 + 29 =
  33. 33.184 + 99 =
  34. 34.61 − 9 =
  35. 35.22 − 9 =
  36. 36.51 − 9 =
  37. 37.67 + 9 =
  38. 38.14 + 9 =
  39. 39.310 + 99 =
  40. 40.742 − 99 =

Answer key

  1. 49
  2. 52
  3. 753
  4. 64
  5. 89
  6. 4
  7. 27
  8. 12
  9. 54
  10. 22
  11. 94
  12. 452
  13. 42
  14. 93
  15. 293
  16. 36
  17. 49
  18. 91
  19. 72
  20. 9
  21. 25
  22. 642
  23. 31
  24. 60
  25. 375
  26. 14
  27. 96
  28. 484
  29. 495
  30. 32
  31. 623
  32. 61
  33. 283
  34. 52
  35. 13
  36. 42
  37. 76
  38. 23
  39. 409
  40. 643

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