A ladder 20 ft long leans against a vertical wall. The top end slides downwards at the rate of 2 ft per second. The rate at which the lower end moves on a horizontal floor when it is 12 ft from the wall is A)frac83; B) frac65; C) frac32; D) frac{17}{4}

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vcalcanofbb · Accepted Answer

The ideal decision is  A)       8    3  From figure,       x    2    +      y    2    =  400        We have             d      y              d      t        =  2     f  t      /    s  e  c      x    2    +      y    2    =  400  Differentiate w.r.t t,   2  x            d      x              d      t        +  2  y            d      y              d      t        =  0  ⇒  x            d      x              d      t        =  −  2  y Now, when   x  =  12  ⇒  y  =  16  ∴  12  ×            d      x              d      t        =  −  2  ×  16    ⇒            d      x              d      t        =  −      8    3

A ladder 20 ft long leans against a vertical wall. The top end slides downwards at the rate of 2 ft per second. The rate at which the lower end moves on a horizontal floor when it is 12 ft from the wall is A)8/3; B)6/5; C)3/2; D)17/4

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