Temperature drops

If the temperature of a city drops 2° every day and increases by 3° every five days, how long does it take to drop to -15° from temperature +5°?

Correct answer:

n =  20 d

Step-by-step explanation:

$$\begin{gathered} t_2=+5 \\ {t}_1=-15{}^{\circ } \\ \Delta =t_2-t_1=5-(-15)=20{}^{\circ } \\ n=\frac{\Delta }{+3-2}=\frac{20}{+3-2}=20\text{d} \end{gathered}$$

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