1Two things to notice first
Waiting isn't about how fast the teller works
You only need two ideas. Watch each one:
Your wait is the stuck time
Wait = how long you stand there before a teller is free. The teller can be lightning fast — but if you're stuck behind people, you still wait.
Some orders are slow
Most people are quick. Once in a while, someone has a huge pile of stuff. You can't tell who from the back — and that one slow order changes everything.
2Two ways to shape the crowd
One shared line vs a line per teller
Same people, same tellers — just lined up two different ways:
Everyone waits together
One snaking line. Whoever's at the front goes to whichever teller opens up next.
You pick and you're stuck
Pick a line and commit. You're stuck with whatever happens in your line.
3Your turn — be the door
Send people in and watch one shared line work
Tap to let a customer in. They join one shared line, and the moment any teller is free, the next person walks straight over. No teller ever sits empty while someone waits. Get a feel for the rule first.
4The fair race
Same crowd, same tellers — only the lines change
Now the real test. The exact same people arrive in the exact same order, and each one takes the exact same time — including two with giant slow orders. We run them once as one shared line, once as a line per teller. Guess first.
Guess before you run it
Same tellers, same customers, same orders — only the lines are arranged differently. Which way gives a shorter average wait?