Sarah Chen had passed every physical challenge at the Riverside Fire Department—climbing ladders with hoses, and simulating rescues. But as she sat in the plain white room at headquarters, she realized this last test would check something different: how well she could think under pressure.
Chief Martinez had said: “Battling fires means making smart choices with limited information when people’s lives are on the line.”
Now looking at three identical electrical switches on a bare wall, Sarah understood why this test mattered so much. In real emergencies, firefighters often had to deal with unfamiliar building systems and make vital decisions about power, gas and water controls without knowing all the consequences.
“This is a real situation,” Chief Martinez’s voice crackled over the intercom. “You’re in a building’s utility room during an emergency. In the next room, three light bulbs depict different building systems. Each switch controls one light bulb, but you don’t know which. You can flip these switches as much as you want from here, but once you open that door to the next room, there’s no going back. So I will meet you in the next room and you need to tell me which switch controls which bulb?”
To everyone’s surprise Sarah walked into the next room a few minutes later and told the Chief which bulb was controlled by which switch. How did Sarah figure it out so accurately?
——— View the answer ———
Sarah found her plan—one that would guarantee the correct solution.
Phase 1: The Plan
She turned Switch 1 ON and left it that way for 10 minutes using her watch to time. After 10 minutes, she turned Switch 1 OFF
She turned Switch 2 ON and left it that way
Switch 3 stayed OFF the whole time
Phase 2: The Check
Sarah took a deep breath and opened the door and stepped into next room. She could easily see:
The bright light: Switch 2 controlled this system (left ON)
The dark but hot light: Switch 1 controlled this system (just turned off still hot)
The dark and cool light: Switch 3 controlled this system (never turned on)
