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A body cools from a temperature 3T to 2T in 10 minutes. The room temperature is T. Assume that Newtons law of cooling is applicable. The temperature of the body at the end of next 10 minutes will be

T
$\dfrac{7}{4}$T
$\dfrac{3}{2}$T
$\dfrac{4}{3}$T
Explanation:

$\triangle T = \triangle T_0e^{–\lambda t}$

$T = 2Te^{–\lambda(10 \ min.)}$

$\triangle T = 2Te^{–\lambda(20 \ min.)} = 2T\left(\dfrac{1}{2}\right)^2 = \dfrac{T}{2}$

$T_f = T + \dfrac{T}{2} = \dfrac{3T}{2}$

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