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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 60 · 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. 1.37 − 9 =
  2. 2.26 + 29 =
  3. 3.23 + 9 =
  4. 4.65 − 29 =
  5. 5.17 − 9 =
  6. 6.29 + 9 =
  7. 7.49 − 29 =
  8. 8.40 − 29 =
  9. 9.434 − 99 =
  10. 10.24 − 19 =
  11. 11.64 − 29 =
  12. 12.355 − 99 =
  13. 13.37 + 19 =
  14. 14.26 + 19 =
  15. 15.491 − 99 =
  16. 16.372 + 99 =
  17. 17.108 − 29 =
  18. 18.69 + 9 =
  19. 19.64 − 19 =
  20. 20.25 + 19 =
  21. 21.79 + 19 =
  22. 22.98 − 29 =
  23. 23.602 + 99 =
  24. 24.106 − 29 =
  25. 25.89 − 19 =
  26. 26.52 − 29 =
  27. 27.62 + 29 =
  28. 28.46 − 19 =
  29. 29.779 − 99 =
  30. 30.447 − 99 =
  31. 31.681 + 99 =
  32. 32.329 + 99 =
  33. 33.63 − 29 =
  34. 34.79 − 9 =
  35. 35.61 + 9 =
  36. 36.18 − 9 =
  37. 37.623 + 99 =
  38. 38.26 − 9 =
  39. 39.26 − 19 =
  40. 40.50 + 19 =

Answer key

  1. 28
  2. 55
  3. 32
  4. 36
  5. 8
  6. 38
  7. 20
  8. 11
  9. 335
  10. 5
  11. 35
  12. 256
  13. 56
  14. 45
  15. 392
  16. 471
  17. 79
  18. 78
  19. 45
  20. 44
  21. 98
  22. 69
  23. 701
  24. 77
  25. 70
  26. 23
  27. 91
  28. 27
  29. 680
  30. 348
  31. 780
  32. 428
  33. 34
  34. 70
  35. 70
  36. 9
  37. 722
  38. 17
  39. 7
  40. 69

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