How to show the arrangement of the blocks in following fashion can have utmost two different colours

You are given 10 boxes, each large enough to contain exactly 10 wooden blocks, and a total of 100 blocks in 10 different colours.There might not be the same number in each colour, so you might not be able to pack the blocks into the boxes in such a way that each bo开发者_JAVA百科x contains only one colour of block. Show that it is possible to pack the blocks into the boxes so that each box contains at most two different colours.

---

Arrange the blocks by color. The smallest group will have no more than 10 blocks. Fill one box with this color, fill the remainder with blocks from the biggest pile. You now have on box less to fill & 1 Color gone. Repeat.

See http://mei.org.uk/images/Nov09_miotm_solution.JPG