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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 509 · 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. 1.34 + 9 =
  2. 2.48 − 29 =
  3. 3.108 − 29 =
  4. 4.58 − 9 =
  5. 5.83 − 19 =
  6. 6.51 − 29 =
  7. 7.45 + 19 =
  8. 8.47 − 29 =
  9. 9.43 + 19 =
  10. 10.56 − 9 =
  11. 11.299 − 99 =
  12. 12.23 − 9 =
  13. 13.14 − 9 =
  14. 14.157 − 99 =
  15. 15.76 − 19 =
  16. 16.63 − 19 =
  17. 17.38 + 9 =
  18. 18.46 − 19 =
  19. 19.41 − 29 =
  20. 20.36 − 19 =
  21. 21.32 − 29 =
  22. 22.371 + 99 =
  23. 23.30 − 19 =
  24. 24.22 + 29 =
  25. 25.77 + 9 =
  26. 26.67 + 19 =
  27. 27.35 + 19 =
  28. 28.31 + 19 =
  29. 29.61 − 29 =
  30. 30.89 − 19 =
  31. 31.647 − 99 =
  32. 32.370 + 99 =
  33. 33.17 − 9 =
  34. 34.77 + 29 =
  35. 35.687 − 99 =
  36. 36.686 + 99 =
  37. 37.76 − 9 =
  38. 38.16 + 29 =
  39. 39.96 − 19 =
  40. 40.30 − 9 =

Answer key

  1. 43
  2. 19
  3. 79
  4. 49
  5. 64
  6. 22
  7. 64
  8. 18
  9. 62
  10. 47
  11. 200
  12. 14
  13. 5
  14. 58
  15. 57
  16. 44
  17. 47
  18. 27
  19. 12
  20. 17
  21. 3
  22. 470
  23. 11
  24. 51
  25. 86
  26. 86
  27. 54
  28. 50
  29. 32
  30. 70
  31. 548
  32. 469
  33. 8
  34. 106
  35. 588
  36. 785
  37. 67
  38. 45
  39. 77
  40. 21

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