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Joshuam1

  • one year ago

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

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  1. Joshuam1
    • one year ago
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    the triangle

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  2. srossd
    • one year ago
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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.

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

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

  5. srossd
    • one year ago
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    Absolutely

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

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

  9. srossd
    • one year ago
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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.

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

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

  12. Joshuam1
    • one year ago
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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.

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

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

  15. Joshuam1
    • one year ago
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    okay :D

  16. Joshuam1
    • one year ago
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    2.77

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

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

  19. srossd
    • one year ago
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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.

  20. Joshuam1
    • one year ago
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    the sqrt is 1.66

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

  22. Joshuam1
    • one year ago
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    how?

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

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

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

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

  27. Joshuam1
    • one year ago
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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

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

  29. srossd
    • one year ago
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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.

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

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

  32. Joshuam1
    • one year ago
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    2.25

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

  34. Joshuam1
    • one year ago
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    oh okay

  35. Joshuam1
    • one year ago
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    so square 54?

  36. Joshuam1
    • one year ago
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    2916

  37. Joshuam1
    • one year ago
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    wait oops my mistake

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

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

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

  41. Joshuam1
    • one year ago
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    alright i got 24

  42. srossd
    • one year ago
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    Yup, nice job

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

  44. srossd
    • one year ago
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    Great, no problem

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