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The side of a cube is decreasing at a rate of 9 millimeters per minute.
At a certain instant, the side is 19 millimeters.
What is the rate of change of the volume of the cube at that instant (in cubic millimeters per minute)?
Choose 1 answer:
(A) -729
(B) -9747
(C) -6859
(D) -3249

The side of a cube is decreasing at a rate of 99 millimeters per minute.\newlineAt a certain instant, the side is 1919 millimeters.\newlineWhat is the rate of change of the volume of the cube at that instant (in cubic millimeters per minute)?\newlineChoose 11 answer:\newline(A) 729-729\newline(B) 9747-9747\newline(C) 6859-6859\newline(D) 3249-3249

Full solution

Q. The side of a cube is decreasing at a rate of 99 millimeters per minute.\newlineAt a certain instant, the side is 1919 millimeters.\newlineWhat is the rate of change of the volume of the cube at that instant (in cubic millimeters per minute)?\newlineChoose 11 answer:\newline(A) 729-729\newline(B) 9747-9747\newline(C) 6859-6859\newline(D) 3249-3249
  1. Volume formula: Volume of a cube formula is V=s3V = s^3, where ss is the side length.
  2. Differentiate volume: Differentiate the volume with respect to time to find the rate of change of volume, dVdt=3s2dsdt\frac{dV}{dt} = 3s^2 \cdot \frac{ds}{dt}.
  3. Plug in values: Plug in the values: s=19mms = 19 \, \text{mm} and dsdt=9mm/min\frac{ds}{dt} = -9 \, \text{mm/min}.
  4. Calculate dVdt\frac{dV}{dt}: Calculate dVdt=3×(19)2×(9)\frac{dV}{dt} = 3 \times (19)^2 \times (-9).
  5. Simplify calculation: Simplify the calculation: dVdt=3×361×(9)\frac{dV}{dt} = 3 \times 361 \times (-9).
  6. Multiply for rate: Multiply to find the rate of change: dVdt=3×361×(9)=1083×(9)\frac{dV}{dt} = 3 \times 361 \times (-9) = 1083 \times (-9).
  7. Final calculation: Final calculation: dVdt=9747mm3/min.\frac{dV}{dt} = -9747 \, \text{mm}^3/\text{min}.

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