Small doubt from PYQ Jee main AOD


Here do we write volume of ice melting as…

  1. V =4/3p(10+x)^3
    OR
  2. V = 4/3p((10+x)^3 - (10)^3)
    In question dV/dt is given as 50cm^3/min…

The second way should be correct as the volume of ice is just on the surface with thickness x
and we have to find dx/dt

Yeah i thought the same… But i m not getting the answer with that…
Instead if i use 1st one, i m getting the correct answer…

I think both methods will give the same answer as when we will differentiate the (-10^3) part will become zero.
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1 Like

Ohhhh yaaa! I did some calculation mistake…
Got it… Thanks!