Question

A Centigrade and Fahrenheit thermometers are dipped in boiling water. The water temperature is lowered until the Fahrenhit thermometer registers $140$. The fall in temperature as registered by centigrade thermometer is ............... .

• A. ${30}^{\circ }$
• B. ${40}^{\circ }$
• C. ${60}^{\circ }$
• D. ${80}^{\circ }$

Answer 1

Answer: (B)

${40}^{\circ }$

Answer is B.

Let us take the temperature of the boiling water be 100 degrees in Celsius scale and 180 degrees in Fahrenheit scale.
That is, $\frac{140-32}{180}=\frac{C}{5}$.
Therefore, $5\times 108=9C,C=60degC.$
Since, the temperature of boiling water is 100 deg C, the required fall is 100 - 60 = 40 degrees C.
Hence, The fall in temperature as registered by centigrade thermometer is 40 degree Celsius.