Answer:
[D]: 4 inches .
_________________________________________Explanation: _________________________________________Formula for Volume of a cone:
__________________________________________________V =

r² *h * (1/3) ;
__________________________________________________Given: V = 251.2 in³ ;
h = 15 in.
π = 3.14 ;
________________________________________Plug in our given values to find, "r" :
_______________________________________________251.2 in³ = (3.14) * r² * (15 in.) * (1/3) ;
_____________________________________ 251.2 in³ = (15.7 in.) * r²
___________________________ Divide each side of the equation by: "(15.7 in.)" ;
_______________________________________________________ 251.2 in³ / (15.7 in.) = (15.7 in.) * r² / (15.7 in.) ;
_________________________________________________________ r² = 16
_______________________Now, take the positive "square root" of EACH SIDE of the equation;
_______________________________________________________to isolate "r" on one side of the equation ; and to solve for "r" ;
_________________________________________________________ √(r²) = √(16 in²) ;
________________________________________________________ r = 4 inches; which is Answer choice: [D] ._______________________________________________________