There are 50 states, and 2/5 start with M A or N, and 2/5 in percent form is 40%. And, 50*40%, which is the same as 50*0.4, equals 20. So twenty states start with M, A, or N.
A quick graph shows the remembrance pattern is not linear because the slope is not the same. Therefore a very likely remembrance pattern will be exponentially related.