Unit 12 · Multi-Step Conditional Reasoning
Three Switches, Four Lights — Which Is Always True?
Lesson 26 of 30
About this lesson
Three switches, four lights. Each switch flip toggles its lights. All start off. Which of the four statements must always be true? The key insight: Red and Green share the same two switches — so they're permanently in sync.
Chapters
Question
Three switches are connected to a set of four lights. When a switch is changed, each of the lights that it controls turns on (if it was off) or off (if it was on).
Switch one controls the red and green lights. Switch two controls the red, green and blue lights. Switch three controls the blue and yellow lights.
If all three switches are off then all four lights are off.
Which one of the following is true?
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