Are my calculations correct for this question?

[bamdavis]

It was found that one ocular micrometer equaled 0.025 mm at 100X power. If the wing of a fruit fly was measured to be 80 ocular micrometer units at a magnification of 100X, what is the length of the wing in mm?

 

I have two answers, but i don't know which is right?

 

0.025mm x 80um = 2mm

 

or

 

0.025 mm x 0.08mm = 0.02 mm

 

in this one i converted the 80 ocular micrometer units to millimeters.

[farmerz_op]

An ocular micrometer is actually a glass disk with a ruled scale; one ocular micrometer unit is the distance between two marks on that scale (length of each subdivision).

 

At 100X power,

One ocular micrometer represents 0.025mm (physical distance).

Therefore,

80 OMU X 0.025mm/OMU = 2mm