Question

on a cold february morning, the temperature of the radiator fluid in stanleys car is - 18°f. when the engine is running, the temperature of the fluid goes up 5.4°f per minute. approximately how long will it take before the radiator fluid temperature reaches 60°f?
7.8 minutes
14.4 minutes
226.8 minutes
421.2 minutes

Explanation:

Step1: Calculate temperature difference

The initial temperature is $- 18^{\circ}F$ and the target temperature is $60^{\circ}F$. The temperature difference $\Delta T=60 - (-18)=60 + 18=78^{\circ}F$.

Step2: Calculate time

The temperature goes up at a rate of $5.4^{\circ}F$ per minute. Let $t$ be the time in minutes. We use the formula $t=\frac{\Delta T}{r}$, where $r = 5.4^{\circ}F$ per minute. So $t=\frac{78}{5.4}\approx14.4$ minutes.

Answer:

14.4 minutes