Question

The temperature at 12 noon was 10${}^{\circ }$C above zero. If it decreases at the rate of 2 ${}^{\circ }$C per hour until midnight, what would be the temperature at 9 p.m.?

• A. -8${}^{\circ }$C
• B. -6${}^{\circ }$C
• C. 8${}^{\circ }$C
• D. 6${}^{\circ }$C

Answer 1

The correct option is A -8${}^{\circ }$C

Given the temperature at 12 noon is ${10}^{\circ }C$.
The temperature decreases at the rate of $2^{\circ }C$ per hour until midnight.
From 12 noon to 9 p.m, it is 9 hours.
$\Rightarrow$ Temperature decrease $=9\times (-2^{\circ }C)=-{18}^{\circ }C$
$\therefore$ Temperature at 9 p.m $={10}^{\circ }C+(-{18}^{\circ }C)$
$=-8^{\circ }C$