CiSRA Puzzle Competition 2010 - Solutions
This puzzle is loosely based on the popular four-fours puzzle, except in reverse.
In the puzzle there are 25 short formulae including 4 boxes, and one long formula including 25 boxes. The first 25 formulae provide the values to put into the 25 boxes at the bottom. The intuitive leap in the puzzle is to notice that the first 25 formulae can be made to produce the numbers 1 to 25, in order, by choosing an appropriate single digit number to put in the boxes.
For each formula, there is a unique digit that will make the formula evaluate to the appropriate number. These digits are then placed in order into the lower formula, as shown below.
Calculating the value of the lower formula gives the number 577345. If you calculated this with a calculator you will have an advantage, as this then needs to be read in calculator spelling (also known as beghilos), by turning the number upside down to produce the word SHELLS.