MathDB
Math Prize 2012 Problem 1

Source:

September 24, 2012

Problem Statement

In the morning, Esther biked from home to school at an average speed of xx miles per hour. In the afternoon, having lent her bike to a friend, Esther walked back home along the same route at an average speed of 3 miles per hour. Her average speed for the round trip was 5 miles per hour. What is the value of xx?