# A physicist must make sure that the temperature of a metal at 0 deg C gets no colder than -80 deg C. The physicist changes the metal's temperature at a steady rate of -4 deg C per hour. For how long can the physicist change the temperature?

Feb 11, 2017

20 hours

#### Explanation:

First let us take the metal as $x$

If the rate of decreasing temperature is -4C/1hr and the physician cannot decrease the temperature beyond -80C.

The time in which he can the physicist change the temperature or the time taken by metal to reach -80C

= $\text{-80C"/ "4C/ 1hr}$

= $- \frac{80}{-} 4$

= 20 hours

so the time in which he can the physicist change the temperature or the time taken by metal to reach -80C is 20 hours