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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 832 · 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. 1.372 − 99 =
  2. 2.737 + 99 =
  3. 3.68 + 29 =
  4. 4.27 − 9 =
  5. 5.76 − 19 =
  6. 6.755 + 99 =
  7. 7.59 − 29 =
  8. 8.77 + 29 =
  9. 9.13 + 29 =
  10. 10.30 − 9 =
  11. 11.96 − 19 =
  12. 12.150 + 99 =
  13. 13.28 + 9 =
  14. 14.457 − 99 =
  15. 15.414 − 99 =
  16. 16.70 − 9 =
  17. 17.52 − 29 =
  18. 18.718 + 99 =
  19. 19.46 − 29 =
  20. 20.51 − 29 =
  21. 21.50 + 9 =
  22. 22.539 + 99 =
  23. 23.42 − 19 =
  24. 24.51 + 9 =
  25. 25.711 + 99 =
  26. 26.289 − 99 =
  27. 27.21 + 9 =
  28. 28.329 + 99 =
  29. 29.440 − 99 =
  30. 30.16 + 19 =
  31. 31.62 − 9 =
  32. 32.32 + 9 =
  33. 33.22 + 19 =
  34. 34.12 + 29 =
  35. 35.269 + 99 =
  36. 36.521 − 99 =
  37. 37.26 + 29 =
  38. 38.61 − 29 =
  39. 39.25 + 9 =
  40. 40.70 − 29 =

Answer key

  1. 273
  2. 836
  3. 97
  4. 18
  5. 57
  6. 854
  7. 30
  8. 106
  9. 42
  10. 21
  11. 77
  12. 249
  13. 37
  14. 358
  15. 315
  16. 61
  17. 23
  18. 817
  19. 17
  20. 22
  21. 59
  22. 638
  23. 23
  24. 60
  25. 810
  26. 190
  27. 30
  28. 428
  29. 341
  30. 35
  31. 53
  32. 41
  33. 41
  34. 41
  35. 368
  36. 422
  37. 55
  38. 32
  39. 34
  40. 41

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