I'm looking at the barometer in my lab as i type this question. it says the pressure is 0.905 atm. what is this pressure expressed in torr?

1 atm is equivalent to 760 torr.

To express 0.905 atm in torr, all you have to do is cross multiplication as follows:

1 atm ... > 760 torr

0.905 atm ... >? torr

pressure = (0.905 * 760) / (1)

pressure = 687.8 torr