MathDB

The numbers

1

15

are each coloured blue or red. Determine all possible colourings that satisfy the following rules: • The number

15

is red. • If numbers

x

and

y

have different colours and

x + y \le 15

, then

x + y

is blue. • If numbers

x

and

y

have different colours and

x \cdot y \le 15

, then

x \cdot y

is red.

Problem Statement