The label on a car's antifreeze container claims to protect the car at temperatures greater than [tex]$-40^{\circ} C$[/tex] and less than [tex]$125^{\circ} C$[/tex]. To convert Celsius temperature to Fahrenheit temperature, the formula is [tex]$C =\frac{5}{9}(F-32)$[/tex]. Write a compound inequality to determine the Fahrenheit temperature range at which the antifreeze protects the car.

A. [tex]\(-40 \ \textless \ \frac{5}{9}(F-32) \ \textless \ 125\)[/tex]

B. [tex]\(-40 \ \textgreater \ \frac{5}{9}(F-32) \ \textgreater \ 125\)[/tex]

C. [tex]\(-40 \ \textless \ \frac{5}{9}(F-32)\)[/tex]

D. [tex]\(\frac{5}{9}(F-32) \ \textless \ 125\)[/tex]



Answer :

To solve this problem, we need to convert the given Celsius temperature range into the corresponding Fahrenheit temperature range. We start with the given compound inequality:

[tex]\[ -40 < \frac{5}{9}(F-32) < 125 \][/tex]

This compound inequality can be broken down into two separate inequalities that we need to solve. Let's solve them step by step:

### Part 1: Solving [tex]\(-40 < \frac{5}{9}(F-32)\)[/tex]

1. Remove the fraction by multiplying all terms by [tex]\(\frac{9}{5}\)[/tex]:
[tex]\[ \left(\frac{9}{5}\right)(-40) < F - 32 \][/tex]

2. Simplify [tex]\(\left(\frac{9}{5}\right)(-40)\)[/tex]:
[tex]\[ \left(\frac{9 \cdot -40}{5}\right) = -72 \][/tex]

So, the inequality now reads:
[tex]\[ -72 < F - 32 \][/tex]

3. Isolate [tex]\(F\)[/tex] by adding 32 to both sides:
[tex]\[ -72 + 32 < F \][/tex]

4. Simplify:
[tex]\[ -40 < F \][/tex]

So, the first part tells us that the Fahrenheit temperature must be greater than [tex]\(-40^\circ F\)[/tex].

### Part 2: Solving [tex]\(\frac{5}{9}(F-32) < 125\)[/tex]

1. Remove the fraction by multiplying all terms by [tex]\(\frac{9}{5}\)[/tex]:
[tex]\[ \left(\frac{9}{5}\right) \left(\frac{5}{9}\right) (F - 32) < \left(\frac{9}{5}\right)125 \][/tex]

2. Simplify the left-hand side (the fractions cancel out):
[tex]\[ F - 32 < \left(\frac{9 \cdot 125}{5}\right) \][/tex]

3. Simplify [tex]\(\left(\frac{9 \cdot 125}{5}\right)\)[/tex]:
[tex]\[ 9 \cdot 25 = 225 \][/tex]

So, the inequality now reads:
[tex]\[ F - 32 < 225 \][/tex]

4. Isolate [tex]\(F\)[/tex] by adding 32 to both sides:
[tex]\[ F < 225 + 32 \][/tex]

5. Simplify:
[tex]\[ F < 257 \][/tex]

### Combining Both Parts
Now combining the results of both parts, we obtain the compound inequality:

[tex]\[ -40 < F < 257 \][/tex]

Therefore, the Fahrenheit temperature range at which the antifreeze protects the car is given by:

[tex]\[ -40 < F < 257 \][/tex]

In summary, the correct compound inequality corresponding to the temperature range mentioned is:

[tex]\[ -40 < \frac{5}{9}(F-32) < 125 \][/tex]