Numberskull is an original puzzle from TopAccolades, designed by David Wolstenholme.
Place the 9 numbers in the bottom-right corner onto the empty white squares, and any of the four arithmetic operators onto the empty grey squares to complete 6 equations - 3 left-to-right and 3 top-to-bottom.
There is always a unique solution. The answer can be found methodically, with no guessing required, using arithmetic and, if appropriate, logic, to determine the positions of the numbers.
Full Help facility.
Always open in Portrait orientation.
Versions for iPhone, iPod Touch, iPad, Nokia, Windows PCs and Macs available from i.compactfun.com.