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cbrusoe

  • 2 years ago

Megan bought an outdoor wall light fixture. The fixture has semicircular ends at the top and bottom as shown. The side of the fixture that faces the wall is open. What is the exterior surface area of the light fixture? Answer 78π in2 84π in2 108π in2 120π in2

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  1. cbrusoe
    • 2 years ago
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  2. apoorvk
    • 2 years ago
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    Just need to find the surface area of each semicircle part, and add 'em up. Or rather, two same semicircles make a circle! so, find out the are of a circle which has a diameter of '12in'. Then, add the area of the rectangular part --> 12x14 - right? What do you think now?

  3. cbrusoe
    • 2 years ago
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    i did something way off ... but im not sure what i found the formula for a cylinder and i plugged in my numbers and calculated it and got 753.6 ....

  4. apoorvk
    • 2 years ago
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    it's not a cylinder! its like a lampshade kinda thing - two semicircular shades, and a rectangular background.

  5. cbrusoe
    • 2 years ago
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    i know but if we added the other half... aha ... ok so what equation do i use?

  6. apoorvk
    • 2 years ago
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    find the area of the rectangular part, then are of each semi-circular shade and add em up!

  7. cbrusoe
    • 2 years ago
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    ok the area of the rectangular part is 168 now i need to find the area of each semi-circular shade ... how do i do that?

  8. cbrusoe
    • 2 years ago
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    sorry ive been working since 6 this morning non-stop... i dont think im trying as hard ... cuz this probably something i should get

  9. apoorvk
    • 2 years ago
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    its okay - i am woozy too :P. area of semi-circle = (1/2) area of circle plus you could think this way - two same semicircles make a circle, so just find the area of the the equivalent circle..

  10. cbrusoe
    • 2 years ago
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    ok well i know the formula for the area of a circle is pi*r2 so since the diamiter is 12 the radius would be 6 plug that in and i got 113.04

  11. cbrusoe
    • 2 years ago
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    uugh but adding those up gives me to big of a number hmmm

  12. apoorvk
    • 2 years ago
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    113 + 168 isn't right?

  13. cbrusoe
    • 2 years ago
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    well it adds up to 281 which isnt one of my options

  14. apoorvk
    • 2 years ago
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    what are your options?

  15. cbrusoe
    • 2 years ago
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    78π in2 84π in2 108π in2 120π in2

  16. apoorvk
    • 2 years ago
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    i am sorry, it's too late here, and i am too woozy - i misunderstood the whole thing - it must be a cylinder itself - i am really sure this time though. @Diyadiya will help you out. Thanks :) and apologies for misguiding - didn't mean it.

  17. Diyadiya
    • 2 years ago
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    I got one answer :D

  18. cbrusoe
    • 2 years ago
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    it's ok thanks for the help =) and ok =)

  19. apoorvk
    • 2 years ago
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    yeah would be -the last one - just help her understand.

  20. Diyadiya
    • 2 years ago
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    First find the area of two semicircles area of semicircle = (pi * r^2)/2 =pi*(6)^2/2 =18pi 2 semicircles =18pi+18pi=36pi

  21. Diyadiya
    • 2 years ago
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    did you understand til this ?

  22. cbrusoe
    • 2 years ago
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    yeahh when we go to the semi circle stuff i think is when i started to get confused

  23. Diyadiya
    • 2 years ago
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    Now its half of a cylinder

  24. Diyadiya
    • 2 years ago
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    and i guess the rectangular part is open

  25. Diyadiya
    • 2 years ago
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    You just have to find the lateral surface area of half of cylinder ( 2*pi*r*h) half cylinder so lateral surface area = 2*pi*r*h/2 =Pi*r*h can you do it?

  26. Diyadiya
    • 2 years ago
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    @cbrusoe ??

  27. cbrusoe
    • 2 years ago
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    yeahh i can do it thank-you =)

  28. Diyadiya
    • 2 years ago
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    can you tell me the lateral surface area of it ?

  29. Diyadiya
    • 2 years ago
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    take your time np

  30. cbrusoe
    • 2 years ago
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    ok when i calculate 2*pi*r*h i got 263.76

  31. Diyadiya
    • 2 years ago
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    don't take the value of pi .. just keep pi like that since your answer contains pi

  32. Diyadiya
    • 2 years ago
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    so what will be the lateral surface area ?

  33. cbrusoe
    • 2 years ago
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    ok so 2*r*h and my diamiter is 12 so radius would be 6 and height is 14 so 2*6*14 = 168pi?

  34. Diyadiya
    • 2 years ago
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    Yes this is the lateral surface area of a cylinder but we have only half of a cylinder so divide it by 2

  35. Diyadiya
    • 2 years ago
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    and add the area of 2 semicircles

  36. cbrusoe
    • 2 years ago
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    ok so 84 plus the are of 2 semicircles

  37. Diyadiya
    • 2 years ago
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    Yes

  38. Diyadiya
    • 2 years ago
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    so what is it ?

  39. cbrusoe
    • 2 years ago
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    120

  40. cbrusoe
    • 2 years ago
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    i may have calcuulated that last part wrong

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