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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 548 · 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. 1.179 + 99 =
  2. 2.232 + 99 =
  3. 3.272 + 99 =
  4. 4.187 − 99 =
  5. 5.46 + 9 =
  6. 6.17 − 9 =
  7. 7.16 − 9 =
  8. 8.223 − 99 =
  9. 9.443 − 99 =
  10. 10.88 − 19 =
  11. 11.230 + 99 =
  12. 12.80 + 19 =
  13. 13.38 − 29 =
  14. 14.77 − 9 =
  15. 15.72 + 19 =
  16. 16.427 + 99 =
  17. 17.92 − 19 =
  18. 18.54 + 19 =
  19. 19.64 + 19 =
  20. 20.82 − 9 =
  21. 21.52 − 9 =
  22. 22.25 + 19 =
  23. 23.23 + 29 =
  24. 24.452 − 99 =
  25. 25.12 + 9 =
  26. 26.302 + 99 =
  27. 27.28 + 19 =
  28. 28.153 − 99 =
  29. 29.197 + 99 =
  30. 30.590 − 99 =
  31. 31.92 − 29 =
  32. 32.33 − 9 =
  33. 33.16 + 9 =
  34. 34.170 + 99 =
  35. 35.41 − 19 =
  36. 36.46 − 29 =
  37. 37.14 − 9 =
  38. 38.77 + 29 =
  39. 39.91 − 19 =
  40. 40.14 + 29 =

Answer key

  1. 278
  2. 331
  3. 371
  4. 88
  5. 55
  6. 8
  7. 7
  8. 124
  9. 344
  10. 69
  11. 329
  12. 99
  13. 9
  14. 68
  15. 91
  16. 526
  17. 73
  18. 73
  19. 83
  20. 73
  21. 43
  22. 44
  23. 52
  24. 353
  25. 21
  26. 401
  27. 47
  28. 54
  29. 296
  30. 491
  31. 63
  32. 24
  33. 25
  34. 269
  35. 22
  36. 17
  37. 5
  38. 106
  39. 72
  40. 43

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