1. Tardigrade
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  3. Physics
  4. 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 :

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Q. A Centigrade and Fahrenheit thermometers are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers a temperature of $140^{\circ}$. The fall of temperature as registered by the Centigrade thermometer is :

AFMCAFMC 2004

Solution:

Fall in temperature in Centigrade thermometer = Initial temperature of boiling water - fall in temperature.
The relation between Centigrade ${ }^{\circ} C$ scale of temperature and Fahrenheit ${ }^{\circ} F$ scale is
$\frac{C}{5}=\frac{F-32}{9}$.
Given, Fahrenheit $F=140^{\circ} F$
$\therefore \frac{C}{5}=\frac{140-32}{9}=\frac{108}{9}=12$
$\Rightarrow C=12 \times 5=60^{\circ} C$
$\therefore $ Fall in temperature in centigrade scale
$=$ initial temperature $-$ full in temperature
$=100^{\circ} C -60^{\circ} C =40^{\circ} C$