Question

A Centigrade and Fahrenheit thermometers are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers a temperature of 140°. The fall of temperature as registered by the Centigrade thermometer is:

• A. $ 80{}^\circ C $
• B. $ 40{}^\circ C $
• C. $ 50{}^\circ C $
• D. $ 90{}^\circ C $

Answer 1

Answer: (B)

The relation between Centigrate $ ^{\circ} $ C scale of temperature and Fahrenheit $ ^{\circ} $ F scale is
$ \frac{C}{5}=\frac{F - 32}{9} $
Fahrenheit F = 140 $ ^{\circ} $ F
= $ \frac{C}{5}=\frac{140 - 32}{9} $
$ ={180}{9}=12 $
$ \Rightarrow C = 12\times5 = 60^{\circ}C $
$ \therefore $ Fall in temperature in centigrade scale
= initial temperature - final temperature
= I00 $ ^{\circ} $ C - 60 $ ^{\circ} $ C = 40 $ ^{\circ} $ C