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Joshuam1 Group Title

Triangle UVW is the pre-image of triangle RST with a scale factor of 3. Find the area of triangle UVW if the area of triangle RST is 9 cm2. 81 cm2 27 cm2 18 cm2 9 cm2

  • one year ago
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  1. Joshuam1 Group Title
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    the triangle

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  2. srossd Group Title
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    An intuitive way to think about this is that area is the square of distance. So, when you scale the distances of the sides by 3, the area scales by 9. So, 9 cm2 becomes 81 cm2.

    • one year ago
  3. Joshuam1 Group Title
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    wow that was simple O_O

    • one year ago
  4. Joshuam1 Group Title
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    I have some similar questions. Think you can have a look?

    • one year ago
  5. srossd Group Title
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    Absolutely

    • one year ago
  6. Joshuam1 Group Title
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    Quadrilateral HIJK is the pre-image of quadrilateral LMNO. Find the scale factor, t.

    • one year ago
  7. Joshuam1 Group Title
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  8. Joshuam1 Group Title
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    the options are 9/4 , 5/3, 9/25, 3/2

    • one year ago
  9. srossd Group Title
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    So, 375/135 = 2.77ish. You know from the last question that that's the square of the scale factor. Square root it and you get 1.66ish. So, 5/3.

    • one year ago
  10. Joshuam1 Group Title
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    okay i have another I'm just working out what you said so i can have it for myself

    • one year ago
  11. srossd Group Title
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    Okay, let me know if you have any questions.

    • one year ago
  12. Joshuam1 Group Title
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    Find WZ if the area of trapezoid ABCD is 225 cm2, the area of trapezoid WXYZ is 81 cm2, and AD is 35 cm.

    • one year ago
  13. Joshuam1 Group Title
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    21 cm 12.6 cm 58.3 cm 97.2 cm

    • one year ago
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  14. srossd Group Title
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    So, find the scale factor first, like I did in the last question.

    • one year ago
  15. Joshuam1 Group Title
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    okay :D

    • one year ago
  16. Joshuam1 Group Title
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    2.77

    • one year ago
  17. srossd Group Title
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    Not quite, you forgot to take the square root.

    • one year ago
  18. Joshuam1 Group Title
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    find the sqrt of 2.77?

    • one year ago
  19. srossd Group Title
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    Right, 225/81=2.77, but that's the ratio of the areas. To turn that into the ratio of lengths, you need the square root.

    • one year ago
  20. Joshuam1 Group Title
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    the sqrt is 1.66

    • one year ago
  21. srossd Group Title
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    Right, so now use that to find WZ.

    • one year ago
  22. Joshuam1 Group Title
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    how?

    • one year ago
  23. srossd Group Title
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    AB/WZ = 1.66

    • one year ago
  24. Joshuam1 Group Title
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    35/21 =1.66

    • one year ago
  25. srossd Group Title
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    Right, so WZ = 21. Good job!

    • one year ago
  26. Joshuam1 Group Title
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    :D sweet 2 more questions

    • one year ago
  27. Joshuam1 Group Title
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    Find the area of the pre-image rectangle QRST if the area of the image rectangle DEFG is 54 cm^2 and the scale factor is 3/2

    • one year ago
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  28. Joshuam1 Group Title
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    216 cm^2 108 cm^2 54 cm^2 24 cm^2

    • one year ago
  29. srossd Group Title
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    Well, with those choices, it's pretty obvious. It has to be less than 54. But still, try and work it out.

    • one year ago
  30. Joshuam1 Group Title
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    okay :D what is the first step?

    • one year ago
  31. srossd Group Title
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    Square the scale factor,s ince you're working with area.

    • one year ago
  32. Joshuam1 Group Title
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    2.25

    • one year ago
  33. srossd Group Title
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    Right. Now, you're going from post image to pre-image, so you have to divide by that.

    • one year ago
  34. Joshuam1 Group Title
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    oh okay

    • one year ago
  35. Joshuam1 Group Title
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    so square 54?

    • one year ago
  36. Joshuam1 Group Title
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    2916

    • one year ago
  37. Joshuam1 Group Title
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    wait oops my mistake

    • one year ago
  38. srossd Group Title
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    Are you doing 54/2.25?

    • one year ago
  39. Joshuam1 Group Title
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    sorry no i divded 54 and 3/2

    • one year ago
  40. srossd Group Title
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    You need to divide by the squared ratio, since you're dealing with area.

    • one year ago
  41. Joshuam1 Group Title
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    alright i got 24

    • one year ago
  42. srossd Group Title
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    Yup, nice job

    • one year ago
  43. Joshuam1 Group Title
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    ty for all your help I am done :D

    • one year ago
  44. srossd Group Title
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    Great, no problem

    • one year ago
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