The minimum number of colours required to paint all sides of a cube so that no two adjacent faces may have the same colour is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 3
Only faces that share an edge must differ in colour. A cube has 6 faces in 3 pairs of opposite faces, and opposite faces never touch, so each pair can take one colour:
Top and bottom: colour 1
Front and back: colour 2
Left and right: colour 3
Two colours are not enough: the top, front and right faces meet at one corner and each touches the other two, so these three need three different colours.