Fluid Mechanics: Differential Hg Manometer

[nicmat42]

Homework Statement

A differential mercury manometer is connected to pipe A containing gasoline (SG=0.65), and to pipe B containing water. Determine the differential reading, h, corresponding to a pressure in A of 20kPa and a vacuum of 150 mm Hg in B.

Homework Equations

Distance from pipe A to fill line is 0.3 m and distance from pipe B to other fill line is 03 m.

The Attempt at a Solution

I have done a few manometer problems before, however, I am not sure what to make of the "vacuum of 150 mm Hg in B". I do not know what this is implying to the problem?
If someone could kindly explain I would be very grateful and will be able to complete the question.
Thanks

 

[Redbelly98]

It sounds like they are talking about the pressure relative to 1 atm (760 mm Hg).

So the "vacuum of 150 mm Hg" means an absolute pressure of (760-150) or 610 mm Hg.

This probably means the 20 kPa pressure is really 1 atm + 20 kPa.