This article for teachers describes several games, found on the
site, all of which have a related structure that can be used to
develop the skills of strategic planning. Solve this Sudoku
puzzle whose clues are in the form of sums of the numbers which
should appear in diagonal opposite cells. A Sudoku with clues
given as sums of entries. The NRICH team are always looking for
new ways to engage teachers and pupils in problem solving. Here
we explain the thinking behind Problem solving is at the heart
of the NRICH site. All the problems give learners opportunities
to learn, develop or use mathematical concepts and skills. Read
here for more information. Find out about Magic Squares in this
article written for students. Why are they magic?! Arrange the
digits 1, 1, 2, 2, 3 and 3 so that between the two 1's there is
one digit, between the two 2's there are two digits, and between
the two 3's there are three digits. A particular technique for
solving Sudoku puzzles, known as "naked pair", is explained in
this easy