Question

A certain freezing process requires the room temperature to be lowered 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

As per the question

A freezing process requires the room temperature to be lowered from 40${}^{\circ }$C at the rate of 5${}^{\circ }$C every hour.

We have to find the room temperature after 10 hours.

The room temperature after first hour = ${40}^{\circ }C-1\times 5^{\circ }C={40}^{\circ }C-5^{\circ }C$

The room temperature after two hours = ${40}^{\circ }C-2\times 5^{\circ }C={40}^{\circ }C-{10}^{\circ }C$

The room temperature after three hours = ${40}^{\circ }C-3\times 5^{\circ }C={40}^{\circ }C-{15}^{\circ }C$

$\therefore$ The room temperature after ten hours = ${40}^{\circ }C-10\times 5^{\circ }C={40}^{\circ }C-{50}^{\circ }C=-{10}^{\circ }C$