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**Posted on 2014-04-27**

## Lights

Source: Maths Jam

You have been taken captive and are blindfolded. There is a table in front of you with four lights on it. Some are on, some are off: you don't know how many and which ones. You need to get either all the lights on or all the lights off to be released. To do this, you can ask your captor to toggle the light switches of some of the lights. You captor will then rotate the table (so you don't know where the lights you toggled now are). Find a sequence of moves which will always lead to your release.

## Princess problem

Source: Maths Jam

A princess lives in a row of 17 rooms. Each day she moves to a room adjacent to the one she wakes up in (eg. If she sleeps in room 5 today, then she will sleep in room 4 or 6 tomorrow). If you are able to find the princess by only opening one door each night then you will become her prince. Can you find her in a finite number of moves?

## Three digit numbers

Source: UKMT Pink Kangaroo 2012

Brigette wrote down a list of all 3-digit numbers. For each of the numbers on her list she found the product of the digits. She then added up all of these products. Which of the following is equal to her total?

**A**\(45\)

**B**\(45^2\)

**C**\(45^3\)

**D**\(2^{45}\)

**E**\(3^{45}\)

If you enjoyed these puzzles, check out Advent calendar 2018,

puzzles about square numbers, or a random puzzle.

puzzles about square numbers, or a random puzzle.