A solid consists of a cone on top of a cylinder with a radius equal to that of the cone. The height of the cone is 60 and the height of the cylinder is 15 . If the volume of the solid is 70 pi, what is the area of the base of the cylinder?

1 Answer
Aug 26, 2016

"Area of Base of cylinder"=2pi

Explanation:

"The Diagram:"

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color(blue)("We know that the volume of the whole solid is" 70pi

(or)

color(red)("The sum of the volumes of the cone and cylinder is " 70pi

"Now lets set up an equation for solving the question"

color(brown)("Volume of cone"=1/3 pir^2h=v_1

color(brown)("Volume of cylinder"=pir^2h=v_2

"(Where "h" is the height and "r" is the radius)"

"Known values of the variables":

color(violet)(h color(violet)("of" color(violet)(v_1=60

color(violet)(h color(violet)("of" color(violet)(v_2=15

"We need to find the value of" pir^2 "which is the base"

:.color(orange)(v_1+v_2=70pi

rarr1/3pir^2h+pir^2h=70pi

rarr1/3pir^(2)60+pir^(2)15=70pi

rarr1/cancel3^1pir^(2)cancel60^20+pir^(2)15=70pi

rarrpir^(2)20+pir^(2)15=70pi

"Rewrite the equation"

rarr20pir^(2)+15pir^(2)=70pi

rarr35pir^2=70pi

rarrpir^2=(cancel70^2pi)/cancel35^1

rArrcolor(green)(pir^2=2pi