The radius of a cone is increasing at a rate of 3 centimeters per second and the height of the cone is decreasing at a rate of 4 centimeters per second.At a certain instant, the radius is 8 centimeters and the height is 10 centimeters.What is the rate of change of the volume of the cone at that instant (in cubic centimeters per second)?Choose 1 answer:(A) −3736π(B) −3224π(C) 3736π(D) 3224πThe volume of a cone with radius r and height h is πr23h.
Q. The radius of a cone is increasing at a rate of 3 centimeters per second and the height of the cone is decreasing at a rate of 4 centimeters per second.At a certain instant, the radius is 8 centimeters and the height is 10 centimeters.What is the rate of change of the volume of the cone at that instant (in cubic centimeters per second)?Choose 1 answer:(A) −3736π(B) −3224π(C) 3736π(D) 3224πThe volume of a cone with radius r and height h is πr23h.
Volume of Cone Formula: The formula for the volume of a cone is V=3πr2h. We need to find dtdV, the rate of change of the volume.
Chain Rule Application: To find dtdV, we use the chain rule from calculus: dtdV=drdV⋅dtdr+dhdV⋅dtdh.
Find dV/dr: First, we find dV/dr. Differentiate V=3πr2h with respect to r, we get dV/dr=32πrh.
Find dhdV: Next, we find dhdV. Differentiate V=3πr2h with respect to h, we get dhdV=3πr2.
Substitute Values: Now we plug in the values for dtdr, dtdh, r, and h. dtdr=3cm/s, dtdh=−4cm/s, r=8cm, and h=10cm.
Calculate First Part: Substitute these values into the equation: dtdV=(32π8×10)×3+(3π82)×(−4).
Calculate Second Part: Calculate the first part: (2⋅π⋅8⋅10)/3⋅3=(2⋅π⋅80)/3⋅3=(160⋅π)cm3/s.
Add Parts Together: Calculate the second part: (π×82)/3×(−4)=(π×64)/3×(−4)=(−256×π)cm3/s.
Add Parts Together: Calculate the second part: (π⋅82)/3⋅(−4)=(π⋅64)/3⋅(−4)=(−256⋅π) cm3/s. Add the two parts together: dtdV=(160⋅π)+(−256⋅π)=(−96⋅π) cm3/s.
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