red riders with speeds and blue riders with speeds . Each tandem bike has one red and one blue rider. Bike speed = max of the two riders' speeds.
Task : Maximize total speed of all bikes. Task : Minimize total speed of all bikes.
Before reading on, think: how would you pair riders for each task? The core idea: only one rider's speed per bike counts, so you want to avoid wasting fast riders. How you pair them determines whether you use or waste fast speeds.