Final answer:
When increasing the magnification from 100x to 400x, the field of view decreases and you can expect to see approximately 2 yeast cells given that 28 were visible at 100x magnification.
Step-by-step explanation:
If a slide has 28 yeast cells in a field of view at 100x magnification, we must consider the change in field of view when increasing the magnification to 400x. Since the area of the field of view decreases with higher magnification, namely, by a factor of the square of the change in magnification, we can calculate the expected number of yeast cells at 400x magnification. The magnification increase from 100x to 400x is by a factor of 4. Therefore, the field of view decreases by a factor of 4 squared, which is 16. So, we can expect to see approximately 28 / 16 = 1.75, which we would round to approximately 2 yeast cells at 400x magnification if the distribution of cells is uniform.