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iwanttogotostanford

  • one year ago

HELP W? ACT PREP: The figure below shows 2 tangent circles such that the 10-centimeter diameter of the smaller circle is equal to the radius of the larger circle. What is the area, in square centimeters, of the shaded region? DRAWN BELOW

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  1. iwanttogotostanford
    • one year ago
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    |dw:1443385130601:dw|

  2. zepdrix
    • one year ago
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    Which part is shaded? :)

  3. iwanttogotostanford
    • one year ago
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    the larger circle only

  4. zepdrix
    • one year ago
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    Inside the big circle, but outside the small one? ah ok

  5. iwanttogotostanford
    • one year ago
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    yep

  6. zepdrix
    • one year ago
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    That's not too bad :) That's simply `the area of the big circle` - `area of the small circle`

  7. zepdrix
    • one year ago
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    You'll have to recall your area formula: \(\large\rm A=\pi r^2\) What is the area of the larger circle? Are you able to figure that out based on the information given?

  8. iwanttogotostanford
    • one year ago
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    yes! so it would be two equations, one pi (10)^2 and then the other pi(10)^2?

  9. zepdrix
    • one year ago
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    Ooo careful! :) They didn't actually tell us the `radius` of the smaller circle.

  10. iwanttogotostanford
    • one year ago
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    oh yeah ok so what do i do?

  11. zepdrix
    • one year ago
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    You have to remember the relationship bebtween `diameter` and `radius`.

  12. iwanttogotostanford
    • one year ago
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    radius is half diameter

  13. zepdrix
    • one year ago
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    Ok good :o Half of 10 is 5. So that gives us the `r` that we want to use for the smaller circle.

  14. iwanttogotostanford
    • one year ago
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    yes

  15. zepdrix
    • one year ago
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    You had your first equation correct, which corresponded to the area of the larger circle \(\large\rm \pi(10)^2\)

  16. zepdrix
    • one year ago
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    So the smaller one, which we've corrected, should be \(\large\rm \pi(5)^2\) ya? :o

  17. iwanttogotostanford
    • one year ago
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    yes

  18. zepdrix
    • one year ago
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    Square those numbers, then subtract the smaller one from the larger one

  19. iwanttogotostanford
    • one year ago
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    i forget do i use pi in the equation orr just leave it until the end

  20. iwanttogotostanford
    • one year ago
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    ok nevermind for my final answer i got 75pi

  21. zepdrix
    • one year ago
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    yay good job \c:/

  22. iwanttogotostanford
    • one year ago
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    thanks

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