Lateral Thinking Puzzle No. 1
You are in a two-storey house where DOWNSTAIRS, there are three light switches.
Each switch controls one of three light-bulbs located UPSTAIRS, but you don't know which switch controls which light. (As you might expect, you cannot see the light-bulbs from downstairs!)
What can you do so that you need to go upstairs just ONCE to determine which switch controls which light?
Forgetting where you left your keys does not mean you are “losing it”
