Median
The sagittal plane divides the mouth into a right and left half.
A median divides any triangle in half.
boundary line
Yes, a baseball does have a plane of symmetry. When sliced in half along its equator, both halves are mirror images of each other.
The value you are referring to is the median. It represents the middle value in a dataset when the values are arranged in ascending or descending order. It divides the dataset into two equal parts, with half of the observations falling above it and half falling below it.
It is a line of symmetry.
The right temporal lobe is on the right half of the brain near the Sagittal plane that divides left and right cerebral hemispheres.
The median is the midpoint of the data set. So half the observations are greater than the median and half are smaller.
The median age is the age that divides a population into two equal halves, with half the population being younger and half being older than that age. It is considered a better measure of the central tendency of a population's age distribution compared to the mean because it is not influenced by extreme values.
You could try the fact that the altitude of an equilateral traingle is also its median so that it divides the base in half. Then Pythagoras does the rest.
The median, by definition, tells you the "half way point" of your data. Exactly half of the observations in the dataset will be less than the median and half will be greater than the median.