Customer Churn Rate

This problem practices a core SaaS metric and tests whether a candidate understands how subscription businesses measure customer loss over time. In an investment banking interview, this matters because churn is a key driver of retention, revenue durability, and valuation, so bankers need to be able to interpret it quickly and explain it clearly. The candidate has to know what belongs in the numerator, what belongs in the denominator, and why the metric is expressed as a percentage of the starting customer base rather than some other figure.