Question

The temperature, at which centigrade and Fahrenheit scales give the same reading (in degrees), is:

• A. $-40$
  
• B. $40$
  
• C. $-30$
  
• D. $30$
  

Answer 1

The correct option is A $-40$

By conversion of temperature formula We know that,

$℉=(℃\times 9/5)+32\left(i\right)℃=(℉-32)\times 5/9\left(ii\right)$

Let $x$ be the reading where both $C$ and $F$ scale gives same value:

$x=5/9\times (x-32)x=\left(5/9\right)x-17.778x-\left(5/9\right)x=-17.7780.44x=-17.778x=-40℃or℉$