Question 12(multiple choice worth 5 points)

(03.06 lc)

the volume of a cone is 251.2 cubic inches. the height of the cone is 15 inches. what is the radius of the cone, rounded to the nearest inch? use π = 3.14.

16 inches
8 inches
6 inches
4 inches

 [D]:  4 inches .
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Explanation: 
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Formula for Volume of a cone:
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V =  r² *h * (1/3) ;
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Given: V = 251.2 in³ ;
           h = 15 in.
           π = 3.14 ;
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Plug in our given values to find, "r" :
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251.2 in³ = (3.14) * r² * (15 in.) * (1/3) ;
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 251.2 in³ = (15.7 in.) * r²
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 Divide each side of the equation by:  "(15.7 in.)" ;
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  251.2 in³ / (15.7 in.) = (15.7 in.) * r² / (15.7 in.) ;
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   r² = 16
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Now, take the positive "square root" of EACH SIDE of the equation;
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to isolate "r" on one side of the equation ; and to solve for "r" ;
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        √(r²) = √(16 in²) ; 
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              r = 4 inches; which is Answer choice:  [D] .
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