Question 21
Tottochan draws a neighbourhood of houses numbered 1 to 9 as shown. In every horizontal row, vertical column and diagonal of three houses, the houses must have different colours. She wants to use as few colours as possible.
1. What is the minimum number of colours for houses 1,5,9?
2. What is the minimum for houses 1,5,9,3?
3. What is the minimum for houses 1,5,9,3,7?
4. Using only the colours assigned to houses 1,5,9,3,7, can she colour every house? If so, give a colouring.
1. What is the minimum number of colours for houses 1,5,9?
2. What is the minimum for houses 1,5,9,3?
3. What is the minimum for houses 1,5,9,3,7?
4. Using only the colours assigned to houses 1,5,9,3,7, can she colour every house? If so, give a colouring.