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jmc

algebra junior

Problem

A ball is dropped from 1000 feet high and always bounces back up half the distance it just fell. After how many bounces will the ball first reach a maximum height less than 1 foot?
Solution
We have a geometric sequence with first term 1000 and common ratio . Any term in this sequence can be represented as , where is the number of bounces (for example, when , , or the height of the bounce). We need to find the smallest such that . Through trial and error, we find that , so it takes bounces for the maximum height to be less than 1 foot.
Final answer
10