When a customer pays 20,youneedtogive15 change. You have two options:
1. One 10andone5
2. Three 5billsWhichisbetter?Alwayspreferoption1(usea10). Why? The 5billismoreversatile.Itcanmakechangefor10 customers. The 10billcanonlyhelpwith20 customers. Save the flexible currency. Here's greedy: use the least flexible bills first. This "save the flexible resource" pattern shows up in many greedy problems. When multiple choices work, pick the one that preserves your options.