Question:
A body takes 4 min. to cool from 61° C to 59°C. If the temperature of the surroundings is 30°C, the time taken by the body to cool from 51°C to 49° C is :
Correct Option: , 4
Solution:
$\frac{61-59}{4}=\mathrm{K}\left(\frac{61+59}{2}-30\right)$ .......(1)
$\frac{51-49}{t}=K\left(\frac{51+49}{2}-30\right)$ ......(2)
Divide (1) & (2)
$\frac{t}{4}=\frac{60-30}{50-30}=\frac{30}{20}$
so, $\mathrm{t}=6$ minutes
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