Question

In a local city, the temperature at noon is -3C The temperature is expected to decrease by 2.5C each hour until the temperature reaches -18C How many hours will it take for the temperature to reach-18C?

Answer 1

After six hours temperature in the city should be -18 °C.

Explanation:

Initial temperature is -3 °C.

Rate of temperature decreasing is 2.5 °C/hour. It means negative value.

Final temperature should be -18 °C.

If we write those data as equation we have:

(-3 °C - 2.5 (°C/h)* t) = -18 °C

We can isolate the value of t, t will be the total hours.

-2.5 t = -18 + 3

-2.5 t = -15

t = (-15)/(-2.5) = 6

t = 6 hours.

After six hours temperature in the city should be -18 °C.

Answer 2

Writing the equation that governs this situation:

-3C - (2.5C/hr)x = -18C

Simplifying, -3 - 2.5x = -18, or 3 + 2.5x = 18

Combining like terms: 2.5x = 18-3 = 15

Then x = 15/2.5 = 6. The temp. will reach -18C after 6 hours.