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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 871 · 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. 1.23 + 29 =
  2. 2.329 − 99 =
  3. 3.46 − 19 =
  4. 4.58 − 29 =
  5. 5.55 + 29 =
  6. 6.14 − 9 =
  7. 7.568 − 99 =
  8. 8.224 + 99 =
  9. 9.45 + 19 =
  10. 10.21 − 9 =
  11. 11.57 + 29 =
  12. 12.19 + 19 =
  13. 13.332 + 99 =
  14. 14.275 − 99 =
  15. 15.45 − 19 =
  16. 16.16 − 9 =
  17. 17.63 − 19 =
  18. 18.78 + 29 =
  19. 19.535 − 99 =
  20. 20.33 + 29 =
  21. 21.64 + 9 =
  22. 22.31 + 9 =
  23. 23.97 − 19 =
  24. 24.612 − 99 =
  25. 25.102 − 29 =
  26. 26.51 + 19 =
  27. 27.60 − 9 =
  28. 28.32 − 9 =
  29. 29.34 − 29 =
  30. 30.330 + 99 =
  31. 31.58 − 19 =
  32. 32.75 + 29 =
  33. 33.320 + 99 =
  34. 34.80 − 9 =
  35. 35.41 + 29 =
  36. 36.76 − 29 =
  37. 37.37 − 29 =
  38. 38.361 + 99 =
  39. 39.399 + 99 =
  40. 40.16 + 19 =

Answer key

  1. 52
  2. 230
  3. 27
  4. 29
  5. 84
  6. 5
  7. 469
  8. 323
  9. 64
  10. 12
  11. 86
  12. 38
  13. 431
  14. 176
  15. 26
  16. 7
  17. 44
  18. 107
  19. 436
  20. 62
  21. 73
  22. 40
  23. 78
  24. 513
  25. 73
  26. 70
  27. 51
  28. 23
  29. 5
  30. 429
  31. 39
  32. 104
  33. 419
  34. 71
  35. 70
  36. 47
  37. 8
  38. 460
  39. 498
  40. 35

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