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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 550 · 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. 1.79 − 19 =
  2. 2.73 + 29 =
  3. 3.27 + 19 =
  4. 4.407 + 99 =
  5. 5.12 + 29 =
  6. 6.273 − 99 =
  7. 7.19 − 9 =
  8. 8.338 − 99 =
  9. 9.697 + 99 =
  10. 10.53 + 19 =
  11. 11.768 + 99 =
  12. 12.53 − 9 =
  13. 13.26 − 9 =
  14. 14.511 − 99 =
  15. 15.70 + 9 =
  16. 16.78 + 9 =
  17. 17.22 + 19 =
  18. 18.52 − 19 =
  19. 19.22 − 19 =
  20. 20.29 + 29 =
  21. 21.92 − 19 =
  22. 22.528 + 99 =
  23. 23.81 − 9 =
  24. 24.36 + 9 =
  25. 25.43 + 29 =
  26. 26.458 − 99 =
  27. 27.87 − 29 =
  28. 28.50 − 19 =
  29. 29.50 − 9 =
  30. 30.73 + 9 =
  31. 31.60 + 19 =
  32. 32.65 + 9 =
  33. 33.42 + 29 =
  34. 34.78 − 19 =
  35. 35.35 − 9 =
  36. 36.43 + 9 =
  37. 37.38 + 9 =
  38. 38.538 − 99 =
  39. 39.29 + 19 =
  40. 40.22 + 29 =

Answer key

  1. 60
  2. 102
  3. 46
  4. 506
  5. 41
  6. 174
  7. 10
  8. 239
  9. 796
  10. 72
  11. 867
  12. 44
  13. 17
  14. 412
  15. 79
  16. 87
  17. 41
  18. 33
  19. 3
  20. 58
  21. 73
  22. 627
  23. 72
  24. 45
  25. 72
  26. 359
  27. 58
  28. 31
  29. 41
  30. 82
  31. 79
  32. 74
  33. 71
  34. 59
  35. 26
  36. 52
  37. 47
  38. 439
  39. 48
  40. 51

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