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Question: Answered & Verified by Expert
A 2m ladder leans against a vertical wall. If the top of the ladder begins to slide down the wall at the rate 25cm/sec , then the rate (in cm/sec.) at which the bottom of the ladder slides away from the wall on the horizontal ground when the top of the ladder is 1 m above the ground is:
MathematicsApplication of DerivativesJEE MainJEE Main 2019 (12 Apr Shift 1)
Options:
  • A 25
  • B 253
  • C 253
  • D 253
Solution:
1185 Upvotes Verified Answer
The correct answer is: 253

dydt=-25cm/sec , dxdt=?
Now, x2+y2=22=4
differentiating w.r.t. t both side
2xdxdt+2ydydt=0 x2+y2=4 when y=1 x2=3x=3
dxdt=-yxdydt
dxdt 3,1=-13×-25=253 cm/sec

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