Question

On Tuesday, the temperature at 6 a.m. was -5 °C. It rose 1.2 °C per hour until noon. From noon until 6 p.m., it dropped 0.8 °C per hour. What was the temperature at 6 p.m.?

Answer 1

The rose on the temperature from 6 a.m. until noon is given by the product between the rate it rises by the amount of hours it took to rise. From 6 a.m. until noon, we have 6 hours

`12-6=6`

And the rate it rose was 1.2 °C per hour, then, the increase in the temperature is given by

`6\cdot1.2=7.2`

The same idea goes from the drop of the temperature from noon to 6 p.m.

Between those instants, we have 6 hours again(6 p.m. = 18h)

`18-12=6`

And the rate it dropped was 0.8 °C per hour. The fall in the temperature is given by

`6\cdot0.8=4.8`

And finally, to get our answer, we just need to add the temperature increase to our initial temperature, and then, subtract the drop we had after.

`T=-5+7.2-4.8=-2.6`

The temperature at 6 p.m. was - 2.6 ºC.