$A$ sphere,a cube,and a disc,all of the same material,quality,and volume,are heated to $600\,^{\circ}C$ and left in air. Which of these will have the lowest rate of cooling?

$A$ body cools from $62^{\circ}C$ to $50^{\circ}C$ in $10$ minutes and to $42^{\circ}C$ in the next $10$ minutes. The temperature of the surrounding is ........ $^{\circ}C$.

In a room where the temperature is $30^{\circ}C$,a body cools from $61^{\circ}C$ to $59^{\circ}C$ in $4$ minutes. The time (in min) taken by the body to cool from $51^{\circ}C$ to $49^{\circ}C$ will be ....... $\text{min}$.

$A$ body cools from $80^{\circ} C$ to $50^{\circ} C$ in $5 \text{ min}$. In the next time of $t \text{ min}$, the body continues to cool from $50^{\circ} C$ to $30^{\circ} C$. The total time taken by the body to cool from $80^{\circ} C$ to $30^{\circ} C$ is
[The temperature of the surroundings is $20^{\circ} C$.] (in $\text{ min}$)

Hot water cools from $60\,^{\circ}C$ to $50\,^{\circ}C$ in the first $10\, min$ and to $42\,^{\circ}C$ in the next $10\, min$. The temperature of the surrounding is ........ $^{\circ}C$.

$A$ body cools down from $75^{\circ}C$ to $60^{\circ}C$ in $10 \text{ minutes}$. It will cool down from $65^{\circ}C$ to $55^{\circ}C$ in a time: