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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 884 · 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. 1.36 − 29 =
  2. 2.546 − 99 =
  3. 3.19 + 19 =
  4. 4.38 − 29 =
  5. 5.29 + 9 =
  6. 6.41 + 19 =
  7. 7.38 + 9 =
  8. 8.60 − 9 =
  9. 9.79 + 19 =
  10. 10.88 − 29 =
  11. 11.21 − 9 =
  12. 12.42 + 9 =
  13. 13.87 − 9 =
  14. 14.24 − 9 =
  15. 15.63 − 9 =
  16. 16.33 + 19 =
  17. 17.379 + 99 =
  18. 18.509 + 99 =
  19. 19.74 + 29 =
  20. 20.382 − 99 =
  21. 21.77 + 9 =
  22. 22.413 + 99 =
  23. 23.789 + 99 =
  24. 24.701 − 99 =
  25. 25.41 − 9 =
  26. 26.582 + 99 =
  27. 27.55 + 29 =
  28. 28.27 − 19 =
  29. 29.68 + 19 =
  30. 30.604 − 99 =
  31. 31.64 + 9 =
  32. 32.76 − 29 =
  33. 33.17 + 29 =
  34. 34.50 − 9 =
  35. 35.580 + 99 =
  36. 36.46 + 9 =
  37. 37.72 + 29 =
  38. 38.230 + 99 =
  39. 39.65 + 9 =
  40. 40.83 − 29 =

Answer key

  1. 7
  2. 447
  3. 38
  4. 9
  5. 38
  6. 60
  7. 47
  8. 51
  9. 98
  10. 59
  11. 12
  12. 51
  13. 78
  14. 15
  15. 54
  16. 52
  17. 478
  18. 608
  19. 103
  20. 283
  21. 86
  22. 512
  23. 888
  24. 602
  25. 32
  26. 681
  27. 84
  28. 8
  29. 87
  30. 505
  31. 73
  32. 47
  33. 46
  34. 41
  35. 679
  36. 55
  37. 101
  38. 329
  39. 74
  40. 54

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