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Joshuam1

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

  • 11 months ago
  • 11 months ago

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  1. Joshuam1
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    the triangle

    • 11 months ago
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  2. srossd
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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.

    • 11 months ago
  3. Joshuam1
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    wow that was simple O_O

    • 11 months ago
  4. Joshuam1
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    I have some similar questions. Think you can have a look?

    • 11 months ago
  5. srossd
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    Absolutely

    • 11 months ago
  6. Joshuam1
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    Quadrilateral HIJK is the pre-image of quadrilateral LMNO. Find the scale factor, t.

    • 11 months ago
  7. Joshuam1
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  8. Joshuam1
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    the options are 9/4 , 5/3, 9/25, 3/2

    • 11 months ago
  9. srossd
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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.

    • 11 months ago
  10. Joshuam1
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    okay i have another I'm just working out what you said so i can have it for myself

    • 11 months ago
  11. srossd
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    Okay, let me know if you have any questions.

    • 11 months ago
  12. Joshuam1
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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.

    • 11 months ago
  13. Joshuam1
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    21 cm 12.6 cm 58.3 cm 97.2 cm

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  14. srossd
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    So, find the scale factor first, like I did in the last question.

    • 11 months ago
  15. Joshuam1
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    okay :D

    • 11 months ago
  16. Joshuam1
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    2.77

    • 11 months ago
  17. srossd
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    Not quite, you forgot to take the square root.

    • 11 months ago
  18. Joshuam1
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    find the sqrt of 2.77?

    • 11 months ago
  19. srossd
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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.

    • 11 months ago
  20. Joshuam1
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    the sqrt is 1.66

    • 11 months ago
  21. srossd
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    Right, so now use that to find WZ.

    • 11 months ago
  22. Joshuam1
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    how?

    • 11 months ago
  23. srossd
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    AB/WZ = 1.66

    • 11 months ago
  24. Joshuam1
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    35/21 =1.66

    • 11 months ago
  25. srossd
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    Right, so WZ = 21. Good job!

    • 11 months ago
  26. Joshuam1
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    :D sweet 2 more questions

    • 11 months ago
  27. Joshuam1
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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

    • 11 months ago
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  28. Joshuam1
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    216 cm^2 108 cm^2 54 cm^2 24 cm^2

    • 11 months ago
  29. srossd
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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.

    • 11 months ago
  30. Joshuam1
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    okay :D what is the first step?

    • 11 months ago
  31. srossd
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    Square the scale factor,s ince you're working with area.

    • 11 months ago
  32. Joshuam1
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    2.25

    • 11 months ago
  33. srossd
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    Right. Now, you're going from post image to pre-image, so you have to divide by that.

    • 11 months ago
  34. Joshuam1
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    oh okay

    • 11 months ago
  35. Joshuam1
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    so square 54?

    • 11 months ago
  36. Joshuam1
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    2916

    • 11 months ago
  37. Joshuam1
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    wait oops my mistake

    • 11 months ago
  38. srossd
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    Are you doing 54/2.25?

    • 11 months ago
  39. Joshuam1
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    sorry no i divded 54 and 3/2

    • 11 months ago
  40. srossd
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    You need to divide by the squared ratio, since you're dealing with area.

    • 11 months ago
  41. Joshuam1
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    alright i got 24

    • 11 months ago
  42. srossd
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    Yup, nice job

    • 11 months ago
  43. Joshuam1
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    ty for all your help I am done :D

    • 11 months ago
  44. srossd
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    Great, no problem

    • 11 months ago
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