when you are computing the total magnification of a
specimen you must multiply the objective lens times
the eyepiece. The eyepiece magnification is usually
10 x.The objective lenses are usually 4x, 10x, and
example: Using the high-power objective lens of (43x),
with an eyepiece of a 10x, the magnification would
be 430x. That means that the specimen is being magnified
430 times its original size.
Here to watch a movie on how to compute magnification.