Negative degrees Celsius

From 1:00 a.m. to 10:00 a.m., the temperature dropped 7°C. From 10:00 a.m. until 4:00 p.m., the temperature then rose 15°C. From 4:00 p.m. to 10:00 p.m., the temperature then dropped 4°C. At 10:00 p.m., the temperature was −14°C. What was the temperature at 1:00 a.m.?

Final Answer:

t₁ =  -18 °C

Step-by-step explanation:

$$\begin{gathered} \Delta t=-7+15-4=4\text{°C} \\ {t}_2=-14\text{°C} \\ {t}_1+\Delta t=t_2 \\ {t}_1=t_2-\Delta t=(-14)-4=-18\text{°C} \end{gathered}$$

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