Lights Out

There are 5 rows numbered 1 to 5 and columns 'A' to 'E', thus making a grid of 25 squares each square representing a bulb. You can 'switch off' or 'switch on' the bulb by just clicking the squares. But however, while doing so all the squares which are adjacent to it, either left or right or below (but not diagonal) it will get its position changed. i.e. if it was 'on' already, it will be 'off ' and vice-versa. The problem is to switch off all the squares, that is, all the bulbs for a given configuration of any assorted arrangement of bulbs already switched on.

For a better visualisation and practial trials please click the following link to enable a Jawa applette.

http://www.geocities.com/jaapsch/puzzles/lightjcl.htm

In the Applette clicking 'mix' will produce the arbitrary configuration of 'switched on' bulbs for you to solve. Clicking 'solve' will help you through the minimum number of moves.

Answer:

Number the rows 1-5, the columns A-E.
a) For each light on row 1, press the button beneath it on row 2 to turn the light off. This way row 1 is completely unlit.
b) Repeat step 'a' for rows 2-4, so that now you only have lights on row 5. This is usually called 'chasing the lights'.
c) If the light at A5 is on, press D1 and E1. If the light at B5 is on, press B1 and E1. If the light at C5 is on, press D1.
d) Repeat steps a-b, chasing the lights down and it will be magically solved.
This method will not solve the puzzle in the shortest possible way, but it is very simple.