Answer:
The temperature decreased by 9 °F in 6 days.
Step-by-step explanation:
Let the number of days it takes for the temperature to decrease by 9 °F be [tex]x[/tex].
Given:
Average daily temperature decreases by [tex]1\frac{1}{2}[/tex] °F.
Decrease of temperature in 1 day = [tex]1\frac{1}{2}[/tex]= 1.5 °F.
∴ Decrease in temperature in x days is [tex]1.5x[/tex].
Now, as per question, decrease in temperature in 'x' days is 9 °F.
Therefore, [tex]1.5x=9[/tex]
[tex]x=\frac{9}{1.5}[/tex]
[tex]x=6[/tex]
Therefore, the temperature decreased by 9 °F in 6 days.
