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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 351 · 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. 1.44 + 9 =
  2. 2.27 − 19 =
  3. 3.589 + 99 =
  4. 4.52 − 19 =
  5. 5.60 + 9 =
  6. 6.87 − 19 =
  7. 7.85 − 19 =
  8. 8.25 + 29 =
  9. 9.51 + 29 =
  10. 10.105 − 29 =
  11. 11.36 − 9 =
  12. 12.79 − 29 =
  13. 13.78 + 19 =
  14. 14.23 + 29 =
  15. 15.54 + 9 =
  16. 16.212 + 99 =
  17. 17.65 − 9 =
  18. 18.49 − 9 =
  19. 19.343 + 99 =
  20. 20.66 + 9 =
  21. 21.26 − 19 =
  22. 22.34 − 29 =
  23. 23.32 + 9 =
  24. 24.356 − 99 =
  25. 25.73 + 9 =
  26. 26.462 − 99 =
  27. 27.696 − 99 =
  28. 28.21 − 9 =
  29. 29.640 − 99 =
  30. 30.13 + 29 =
  31. 31.12 + 19 =
  32. 32.50 − 9 =
  33. 33.67 − 29 =
  34. 34.191 + 99 =
  35. 35.595 − 99 =
  36. 36.41 + 9 =
  37. 37.75 − 9 =
  38. 38.75 − 29 =
  39. 39.708 − 99 =
  40. 40.16 + 9 =

Answer key

  1. 53
  2. 8
  3. 688
  4. 33
  5. 69
  6. 68
  7. 66
  8. 54
  9. 80
  10. 76
  11. 27
  12. 50
  13. 97
  14. 52
  15. 63
  16. 311
  17. 56
  18. 40
  19. 442
  20. 75
  21. 7
  22. 5
  23. 41
  24. 257
  25. 82
  26. 363
  27. 597
  28. 12
  29. 541
  30. 42
  31. 31
  32. 41
  33. 38
  34. 290
  35. 496
  36. 50
  37. 66
  38. 46
  39. 609
  40. 25

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