Question

A certain freezing process lowers the temperature from 40${}^{\circ }$C at the rate of 5${}^{\circ }$C every hour. What is the room temperature after 10 hours?

• A. 0${}^{\circ }$C
• B. -5${}^{\circ }$C
• C. -10${}^{\circ }$C
• D. -15${}^{\circ }$C

Answer 1

The correct option is C

-10${}^{\circ }$C

Initial temperature of room = 40${}^{\circ }$C
Given that the temperature lowers at the rate of 5${}^{\circ }$C every hour.
So, the temperature after one hour will be (40 - 5)${}^{\circ }$C
The temperature after two hours will be (40 - 5 - 5)${}^{\circ }$C i.e. 40${}^{\circ }$C - [(5)${}^{\circ }$C $\times$2]
Similarly, after 10 hours, the temperature will be 40${}^{\circ }$C - [(5${}^{\circ }$C)$\times$10]
= 40${}^{\circ }$C - 50${}^{\circ }$C = -10${}^{\circ }$C
Therefore, after 10 hours, the room temperature will be -10${}^{\circ }$C