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A 5-meter ladder is sliding down a vertical wall so the distance between the bottom of the ladder and the wall is increasing at 6 meters per minute.
At a certain instant, the top of the ladder is 3 meters from the ground.
What is the rate of change of the area formed by the ladder at that instant (in square meters per minute)?
Choose 1 answer:
(A) 6
(B) -14
(C) 
18
(D) -7

A 55-meter ladder is sliding down a vertical wall so the distance between the bottom of the ladder and the wall is increasing at 66 meters per minute.\newlineAt a certain instant, the top of the ladder is 33 meters from the ground.\newlineWhat is the rate of change of the area formed by the ladder at that instant (in square meters per minute)?\newlineChoose 11 answer:\newline(A) 66\newline(B) 14-14\newline(C) 18 \mathbf{1 8} \newline(D) 7-7

Full solution

Q. A 55-meter ladder is sliding down a vertical wall so the distance between the bottom of the ladder and the wall is increasing at 66 meters per minute.\newlineAt a certain instant, the top of the ladder is 33 meters from the ground.\newlineWhat is the rate of change of the area formed by the ladder at that instant (in square meters per minute)?\newlineChoose 11 answer:\newline(A) 66\newline(B) 14-14\newline(C) 18 \mathbf{1 8} \newline(D) 7-7
  1. Form Right Triangle: The ladder, wall, and ground form a right triangle. The ladder is the hypotenuse, and the distance from the wall is one leg, which is increasing at 66 meters per minute. The other leg is the height from the ground to the top of the ladder, which is 33 meters.
  2. Calculate Area: Let's call the distance from the wall to the bottom of the ladder xx meters. The area AA of the triangle formed by the ladder, wall, and ground is (12)×x×3(\frac{1}{2}) \times x \times 3.
  3. Differentiate Area: Differentiate the area with respect to time to find the rate of change of the area, dAdt\frac{dA}{dt}. dAdt=12×3×dxdt\frac{dA}{dt} = \frac{1}{2} \times 3 \times \frac{dx}{dt}.
  4. Find Rate of Change: We know dxdt\frac{dx}{dt}, the rate at which the bottom of the ladder moves away from the wall, is 66 meters per minute. So, dAdt=12×3×6\frac{dA}{dt} = \frac{1}{2} \times 3 \times 6.
  5. Calculate dAdt\frac{dA}{dt}: Calculate dAdt\frac{dA}{dt}: dAdt=(12)×3×6=3×6=18\frac{dA}{dt} = \left(\frac{1}{2}\right) \times 3 \times 6 = 3 \times 6 = 18 square meters per minute.

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