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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 819 · 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. 1.42 + 9 =
  2. 2.542 − 99 =
  3. 3.72 + 19 =
  4. 4.45 − 29 =
  5. 5.84 − 29 =
  6. 6.73 + 19 =
  7. 7.453 − 99 =
  8. 8.32 + 19 =
  9. 9.38 − 29 =
  10. 10.33 − 19 =
  11. 11.364 + 99 =
  12. 12.259 − 99 =
  13. 13.76 + 19 =
  14. 14.80 − 9 =
  15. 15.87 − 19 =
  16. 16.65 + 9 =
  17. 17.27 − 19 =
  18. 18.38 + 19 =
  19. 19.16 + 29 =
  20. 20.98 − 19 =
  21. 21.29 + 29 =
  22. 22.51 − 19 =
  23. 23.488 + 99 =
  24. 24.37 + 19 =
  25. 25.48 + 19 =
  26. 26.96 − 19 =
  27. 27.77 − 9 =
  28. 28.44 + 9 =
  29. 29.49 + 19 =
  30. 30.17 + 9 =
  31. 31.53 − 9 =
  32. 32.46 + 9 =
  33. 33.33 + 29 =
  34. 34.99 − 29 =
  35. 35.26 − 9 =
  36. 36.23 + 9 =
  37. 37.47 + 9 =
  38. 38.16 + 19 =
  39. 39.789 + 99 =
  40. 40.749 + 99 =

Answer key

  1. 51
  2. 443
  3. 91
  4. 16
  5. 55
  6. 92
  7. 354
  8. 51
  9. 9
  10. 14
  11. 463
  12. 160
  13. 95
  14. 71
  15. 68
  16. 74
  17. 8
  18. 57
  19. 45
  20. 79
  21. 58
  22. 32
  23. 587
  24. 56
  25. 67
  26. 77
  27. 68
  28. 53
  29. 68
  30. 26
  31. 44
  32. 55
  33. 62
  34. 70
  35. 17
  36. 32
  37. 56
  38. 35
  39. 888
  40. 848

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