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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 11 · 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. 1.56 − 29 =
  2. 2.73 − 19 =
  3. 3.25 + 19 =
  4. 4.69 + 9 =
  5. 5.36 + 9 =
  6. 6.75 + 19 =
  7. 7.61 + 19 =
  8. 8.51 − 9 =
  9. 9.216 − 99 =
  10. 10.50 − 29 =
  11. 11.15 + 29 =
  12. 12.51 + 29 =
  13. 13.20 − 9 =
  14. 14.175 + 99 =
  15. 15.191 − 99 =
  16. 16.64 − 19 =
  17. 17.23 − 19 =
  18. 18.46 − 9 =
  19. 19.55 + 19 =
  20. 20.17 + 19 =
  21. 21.643 + 99 =
  22. 22.62 + 9 =
  23. 23.44 − 19 =
  24. 24.379 + 99 =
  25. 25.595 − 99 =
  26. 26.67 − 29 =
  27. 27.54 − 29 =
  28. 28.25 − 9 =
  29. 29.88 − 9 =
  30. 30.361 + 99 =
  31. 31.52 + 19 =
  32. 32.87 − 29 =
  33. 33.185 + 99 =
  34. 34.255 + 99 =
  35. 35.29 + 9 =
  36. 36.26 + 9 =
  37. 37.77 + 29 =
  38. 38.316 + 99 =
  39. 39.70 + 29 =
  40. 40.77 − 19 =

Answer key

  1. 27
  2. 54
  3. 44
  4. 78
  5. 45
  6. 94
  7. 80
  8. 42
  9. 117
  10. 21
  11. 44
  12. 80
  13. 11
  14. 274
  15. 92
  16. 45
  17. 4
  18. 37
  19. 74
  20. 36
  21. 742
  22. 71
  23. 25
  24. 478
  25. 496
  26. 38
  27. 25
  28. 16
  29. 79
  30. 460
  31. 71
  32. 58
  33. 284
  34. 354
  35. 38
  36. 35
  37. 106
  38. 415
  39. 99
  40. 58

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