A centigrade and a Fehrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fehrenheit thermometer registers `140^(@)F` . What is the fall in temperature as register by the centigrade thermometer

Options

A. `30^(@)`
B. `40^(@)`
C. `60^(@)`
D. `80^(@)`

Answer

B

Explanation

The relation between Centigrade and Fahrenheit scale is as follows:
`C= (5)/(9) (F- 32)`
Here the Fahrenheit temperature is `140^(@)F`, so
`T_("final") = (5)/(9) (140-32) rArr T_("final") = 60^(@)C`
The fall in temperature from the boiling point
`= 100^(@)C - 60^(@)C = 40^(@)C`
`rArr` b is correct