A cup of tea cools from $65.5^o C to 62.5 ^o C$ in one minute in a room of $22.5 ^o C$. How long will the same cup of tea take, in.............. minutes, to cool from $46.50^o C to 40.5 ^o C$ in the same room ? (choose nearest value)
Diffcult
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(d) $\frac{{65.5 - 62.5}}{1} = K\left( {\frac{{65.5 + 62.5}}{2} - 22.5} \right)$ ==> $K = \frac{3}{{41.5}}$
And again $\frac{{46.5 - 40.5}}{t} = \frac{3}{{41.5}}\left( {\frac{{46.5 + 40.5}}{2} - 22.5} \right)$
==> $\frac{6}{t} = \frac{3}{{41.5}} \times 21$ ==> $t = \frac{{82}}{{21}}\tilde - 4$ $minute.$
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