Red Even

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

You have 4 even numbers and 5 odd numbers and all the totals are odd. Think of the red counters as even numbers and the blues as odds. If diagonals can have any total then all three configurations give equivalent solutions because one can be transformed into another by interchanging rows or interchanging columns. If diagonals also have prime totals then only configuration (a) is possible

Published May 2002.