The temperature 17

The temperature was -5 Celsius at 6 AM. It increased by a speed of three degrees every hour for six hours. The temperature then increased 1 1/2° every hour for five hours. What was the temperature at 5 PM?

Correct answer:

t₂ =  20 ¹⁄₂ = 41/2 °C

Step-by-step explanation:

$$\begin{gathered} t_1=-5\text{°C} \\ {\Delta }_1=3\text{°C} \\ {\Delta }_2=1\frac{1}{2}=1+\frac{1}{2}=\frac{1\cdot 2+1}{2}=\frac{2+1}{2}=\frac{3}{2}=1.5\text{°C} \\ {t}_2=t_1+{\Delta }_1\cdot 6+{\Delta }_2\cdot 5=(-5)+3\cdot 6+\frac{3}{2}\cdot 5=\frac{41}{2}\text{°C}=20\frac{1}{2}\text{°C}=20.5\text{°C} \end{gathered}$$

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