Question
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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.)

Ask by Wyatt Warren. in the United States
Jan 25,2025

Real Tutor Solution

Tutor-Verified Answer

Answer

The area of the puddle is increasing at approximately 11.3 square inches per minute.

Solution

To find the rate at which the area of the puddle is growing, we'll use calculus related to the area of a circle. 1. **Area of a Circle:** \[ A = \pi r^2 \] 2. **Differentiate with respect to time (t):** \[ \frac{dA}{dt} = 2\pi r \frac{dr}{dt} \] 3. **Given Values:** - \(\frac{dr}{dt} = 0.3\) inches per minute - Radius \(r = 6\) inches 4. **Plug in the values:** \[ \frac{dA}{dt} = 2 \pi \times 6 \times 0.3 = 3.6\pi \] 5. **Calculate the numerical value:** \[ 3.6\pi \approx 3.6 \times 3.1416 \approx 11.3097 \text{ square inches per minute} \] 6. **Round to one decimal place:** \[ \frac{dA}{dt} \approx 11.3 \text{ square inches per minute} \] **Answer:** The area is increasing at approximately 11.3 in² per minute.

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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.

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