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?
-
A.
6.0mm -
B.
18.0mm -
C.
30.0mm -
D.
60.0mm -
E.
120.0mm