The radius of a circular puddle of water is growing at a rate of 0.3 inches per minute. Find the rate at which the area of the puddle is growing when the radius of the puddle is 6 inches. (Round your answer to one decimal place.)
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The Deep Dive
To find the rate at which the area of the circular puddle is growing, we can use the formula for the area of a circle, A = πr². To find how fast the area is changing with respect to time (dA/dt), we can use implicit differentiation. First, differentiate A with respect to time (t): dA/dt = d/dr(πr²) * dr/dt = 2πr * dr/dt. Given the radius (r) is 6 inches and the rate of growth of the radius (dr/dt) is 0.3 inches/minute, we plug these values into the equation: dA/dt = 2π(6 inches)(0.3 inches/minute). This simplifies to: dA/dt = 3.6π inches²/minute. Now, applying the value of π: dA/dt ≈ 11.3 inches²/minute (rounded to one decimal place). So, the area of the puddle is growing at about 11.3 square inches per minute when the radius is 6 inches.