A 39-meter ladder is sliding down a vertical wall so the distance between the bottom of the ladder and the wall is increasing at 10 meters per minute.At a certain instant, the bottom of the ladder is 36 meters from the wall.What is the rate of change of the distance between the top of the ladder and the ground at that instant (in meters per minute)?Choose 1 answer:(A) −625(B) −12(C) −10(D) −24
Q. A 39-meter ladder is sliding down a vertical wall so the distance between the bottom of the ladder and the wall is increasing at 10 meters per minute.At a certain instant, the bottom of the ladder is 36 meters from the wall.What is the rate of change of the distance between the top of the ladder and the ground at that instant (in meters per minute)?Choose 1 answer:(A) −625(B) −12(C) −10(D) −24
Triangle Description: We're dealing with a right triangle where the ladder is the hypotenuse, the distance from the wall is one leg, and the height of the ladder above the ground is the other leg.
Variable Assignment: Let's call the distance from the wall to the bottom of the ladder x, and the height of the ladder above the ground y.
Pythagorean Theorem: According to the Pythagorean theorem, we have x2+y2=392, since the ladder is 39 meters long.
Differentiation: Differentiate both sides of the equation with respect to time t to find the rates of change. We get 2xdtdx+2ydtdy=0, because the length of the ladder is constant, so dtd(392)=0.
Given Rates: We know that dtdx, the rate at which x is changing, is 10 meters per minute. We need to find dtdy.
Finding y: Plug in the values we know: x=36 meters, dtdx=10 meters/minute. We need to find y before we can solve for dtdy.
Calculating y: Using the Pythagorean theorem again, we find y by solving 362+y2=392. This gives us y2=392−362.
Solving for dtdy: Calculate y2: y2=1521−1296, which gives us y2=225.
Simplify Equation: Take the square root of y2 to find y: y=225, which gives us y=15 meters.
Solving for dtdy: Now we can solve for dtdy using the differentiated Pythagorean theorem: 2⋅36⋅(10)+2⋅15⋅(dtdy)=0.
Final Calculation: Simplify the equation: 720+30(dtdy)=0.
Final Calculation: Simplify the equation: 720+30dtdy=0. Solve for dtdy: 30dtdy=−720.
Final Calculation: Simplify the equation: 720+30dtdy=0. Solve for dtdy: 30dtdy=−720. Divide both sides by 30 to find dtdy: dtdy=−720/30.
Final Calculation: Simplify the equation: 720+30dtdy=0. Solve for dtdy: 30dtdy=−720. Divide both sides by 30 to find dtdy: dtdy=−720/30. Calculate dtdy: dtdy=−24 meters/minute.
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