The lower and upper fixed points of a mercury-in-glass thermometer are marked X and 180 mm respectively. On a particular day the mercury meniscus in the thermometer rises to 60mm. If the corresponding reading on a Celsius scale is 20 ° C, what is the value X?
6.0mm
18.0mm
30.0mm
60.0mm
120.0mm
Correct answer is C
No explanation has been provided for this answer.