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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 734 · 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. 1.22 + 29 =
  2. 2.19 + 9 =
  3. 3.27 + 29 =
  4. 4.33 − 9 =
  5. 5.41 − 9 =
  6. 6.32 − 29 =
  7. 7.81 − 9 =
  8. 8.63 − 19 =
  9. 9.26 − 9 =
  10. 10.55 + 19 =
  11. 11.576 + 99 =
  12. 12.23 + 9 =
  13. 13.50 + 9 =
  14. 14.156 + 99 =
  15. 15.37 + 19 =
  16. 16.53 − 19 =
  17. 17.29 + 19 =
  18. 18.20 − 9 =
  19. 19.43 + 9 =
  20. 20.820 − 99 =
  21. 21.72 + 9 =
  22. 22.51 + 19 =
  23. 23.78 + 9 =
  24. 24.372 + 99 =
  25. 25.53 − 29 =
  26. 26.67 + 19 =
  27. 27.38 + 19 =
  28. 28.51 + 29 =
  29. 29.19 + 19 =
  30. 30.77 + 9 =
  31. 31.49 + 9 =
  32. 32.33 − 29 =
  33. 33.125 + 99 =
  34. 34.257 − 99 =
  35. 35.253 + 99 =
  36. 36.655 + 99 =
  37. 37.757 − 99 =
  38. 38.55 − 29 =
  39. 39.59 − 9 =
  40. 40.60 + 29 =

Answer key

  1. 51
  2. 28
  3. 56
  4. 24
  5. 32
  6. 3
  7. 72
  8. 44
  9. 17
  10. 74
  11. 675
  12. 32
  13. 59
  14. 255
  15. 56
  16. 34
  17. 48
  18. 11
  19. 52
  20. 721
  21. 81
  22. 70
  23. 87
  24. 471
  25. 24
  26. 86
  27. 57
  28. 80
  29. 38
  30. 86
  31. 58
  32. 4
  33. 224
  34. 158
  35. 352
  36. 754
  37. 658
  38. 26
  39. 50
  40. 89

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