Question

The formula $F=\frac{9}{5}C+32$ relates any Centigrade reading to its corresponding Fahrenheit reading. For what temperature is the reading the same on both scales?

• A. ${40}^o$
• B. $0^o$
• C. $-{40}^o$
• D. ${32}^o$
• E. ${73}^o$

Answer 1

The correct option is C $-{40}^o$

Given, $F=\frac{9}{5}C+32$ and $F=C$
So, we have $F=\frac{9}{5}F+32$

$\Rightarrow \frac{4}{5}F=-32$
$\Rightarrow F=-32\times \frac{5}{4}=-40$