Final answer:
The total magnification while using a 40x high-power objective lens on a microscope is 400x, calculated by multiplying the objective lens magnification by the eyepiece lens, which is typically 10x.
Step-by-step explanation:
The total magnification when looking through a microscope using a high-power objective lens of 40x is determined by multiplying the magnification of the objective lens by the magnification of the eyepiece lens, which is typically 10x. Therefore, to calculate the total magnification, you would perform the following multiplication: 40x (objective lens) × 10x (eyepiece lens), which equals a total magnification of 400x.
Given the options, the correct answer is E) 400x.