Which lights are ON?
Tap a bulb to switch it on or off.
Clues
0/2 clues met
- The red light is ON in row A.
- Exactly one light is ON.
Text version of this lesson
Switch bulbs on and off until every clue holds at the same time.
Key takeaway: Clues are not steps in a recipe: every one of them has to be true of the finished board.
Question 1
Tap a bulb to switch it on or off.
Which lights are ON?
Show answer and explanation
Why: One clue fixed a bulb, the other closed off every alternative. Together they leave a single grid.
Hint: The first clue names one bulb exactly. Switch it on.
Question 2
Which lights are ON?
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Why: Counting first pinned the total at three, and that made the rest forced.
Hint: One light per colour means three lights are ON in total.
Question 3
Which lights are ON?
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Why: A negative clue is still information: ruling one option out can decide the whole row.
Hint: Red is taken by row A, so rows B and C share yellow and purple.
Question 4
Which lights are ON?
Show answer and explanation
Why: Only 3 + 1 works: the grid is three columns wide, so row A cannot hold four.
Hint: Rows A and C have to share all four lights, because row B holds none.
Question 5
Which lights are ON?
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Why: Clues that switch things off are the fastest way to shrink a grid.
Hint: With row A dark and yellow dark, only four bulbs remain in play.
Question 6
Which lights are ON?
Show answer and explanation
Why: Once the red quota is filled, every remaining row is forced onto the only colour left.
Hint: Purple is out, so every row shows red or yellow.