The challenge
A person lives on the twentieth floor. Each morning they take the elevator down. Returning home, they usually ride to the twelfth floor and walk the rest, but on rainy days they ride all the way to the twentieth. Why?
Elevator Riddle: Why Stop at Floor 12?
Solve this easy lateral challenge, then compare your reasoning with the hint, checked answer, verification, and variation.
Hint
What changes on a rainy day besides the weather?
A reach problem, not a preference
The person is short and can reach only the twelfth-floor button. On rainy days, an umbrella lets them press the twentieth-floor button.
The exercise story adds an unsupported motive
Assuming the resident chooses to walk for exercise conflicts with the rainy-day exception and does not explain why the twelfth floor is consistent.
Facts that support the explanation
- Notice that the resident reaches the ground-floor button when leaving home.
- Ask what prevents access to buttons above the twelfth floor on the return trip.
- Use the rainy-day object as the extra reach needed to press the twentieth-floor button.
Explain the rainy-day exception
Short reach explains the normal stop, the umbrella explains the rainy-day change, and both facts preserve the stated destination.
Replace the hidden assumption
Question the assumed capabilities of the actor, not only the mechanics of the setting.
How confident were you?
Separate destination from capability
Separate what the story states from what it merely suggests. The resident wants to reach the twentieth floor, so look for a changing capability rather than a changing destination.
Find another way the capability could change
What other ordinary circumstance could let the resident reach the higher button without changing the explanation's core assumption?
Study assumption mapping for the reusable method behind this challenge. Then explore the lateral thinking challenges learning path for connected examples and practice.