College

Celsius and Fahrenheit

The formula to convert from Celsius to Fahrenheit is [tex]F = \frac{9}{5} C + 32[/tex]. Use this formula to complete the statements below. Round your answers to the nearest tenth as needed.

1. If the temperature is 71 degrees Fahrenheit, that is equivalent to [tex]\square[/tex] degrees Celsius.

2. If the temperature is 39 degrees Celsius, that is equivalent to [tex]\square[/tex] degrees Fahrenheit.

Answer :

We start with the conversion formulas between Celsius ([tex]$C$[/tex]) and Fahrenheit ([tex]$F$[/tex]). The formula to convert from Celsius to Fahrenheit is

[tex]$$
F = \frac{9}{5} C + 32.
$$[/tex]

### Converting Fahrenheit to Celsius

To convert Fahrenheit to Celsius, we first solve the above formula for [tex]$C$[/tex]. Subtracting 32 from both sides gives

[tex]$$
F - 32 = \frac{9}{5} C.
$$[/tex]

Multiplying both sides by [tex]$\frac{5}{9}$[/tex], we have

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

For [tex]$F = 71$[/tex] degrees Fahrenheit, substitute into the equation:

[tex]$$
C = \frac{5}{9} (71 - 32) = \frac{5}{9} \times 39.
$$[/tex]

Calculating the expression:

[tex]$$
\frac{5}{9} \times 39 = \frac{195}{9} \approx 21.6667.
$$[/tex]

Rounded to the nearest tenth, the temperature in Celsius is

[tex]$$
21.7^\circ C.
$$[/tex]

### Converting Celsius to Fahrenheit

Using the original formula for the reverse conversion, for [tex]$C = 39$[/tex] degrees Celsius, we have

[tex]$$
F = \frac{9}{5} \times 39 + 32.
$$[/tex]

First, multiply:

[tex]$$
\frac{9}{5} \times 39 \approx 70.2.
$$[/tex]

Then add 32:

[tex]$$
70.2 + 32 = 102.2.
$$[/tex]

Thus, the temperature in Fahrenheit is

[tex]$$
102.2^\circ F.
$$[/tex]

### Final Answers

- If the temperature is [tex]$71^\circ F$[/tex], it is equivalent to approximately [tex]$21.7^\circ C$[/tex].
- If the temperature is [tex]$39^\circ C$[/tex], it is equivalent to approximately [tex]$102.2^\circ F$[/tex].

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