Question

For a scientific experiment, a physicist must make sure that the temperature of a metal does not get colder than −78 °C. The physicist changes the metal's temperature at a steady rate of −3 °C per hour.
Let t represent temperature in degrees Celsius. Enter an inequality. Use the fact that the rate of change in temperature times the number of seconds equals the final temperature.


Solve the inequality in the first part. How long will it take the physicist to change the temperature of the metal?


The physicist has to repeat the experiment if the metal gets cooler than −78 °C. How many hours would the physicist have to cool the metal for this to happen?

Answer 1

-3t < -78 
÷-3      ÷-3
_________
t > 26

78÷26=3