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