A ball is dropped from a height of 10 feet. After bouncing, it reaches a height that is 80% of the height from which it was dropped. This bouncing trend continues until the ball comes to a rest. Show that the distance the ball falls on each drop follows a geometric sequence.

Suppose you are choosing a 6-digit personal access code. this code is made up of 4 digits chosen from 1 to 9, followed by 2 letters chosen from a to z. any of these digits or letters can be repeated. find the total number of personal access codes that can be formed. 492,804 341,172 39,917,124 4,435,236