Art of Problem Solving

2020 IMO Problems/Problem 3: Difference between revisions

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Problem 3. There are 4n pebbles of weights 1, 2, 3, . . . , 4n. Each pebble is coloured in one of n
== Problem ==
colours and there are four pebbles of each colour. Show that we can arrange the pebbles into two
There are <math>4n</math> pebbles of weights <math>1, 2, 3, . . . , 4n</math>. Each pebble is colored in one of <math>n</math> colors and there are four pebbles of each color. Show that we can arrange the pebbles into two piles so that the following two conditions are both satisfied:
piles so that the following two conditions are both satisfied:
* The total weights of both piles are the same.
The total weights of both piles are the same.
* Each pile contains two pebbles of each color.
Each pile contains two pebbles of each colour.


== Video solution ==
== Video solution ==


https://youtu.be/bDHtM1wijbY [Video covers all day 1 problems]
https://youtu.be/bDHtM1wijbY [Video covers all day 1 problems]

Revision as of 10:25, 14 May 2021

Problem

There are $4n$ pebbles of weights $1, 2, 3, . . . , 4n$. Each pebble is colored in one of $n$ colors and there are four pebbles of each color. Show that we can arrange the pebbles into two piles so that the following two conditions are both satisfied:

  • The total weights of both piles are the same.
  • Each pile contains two pebbles of each color.

Video solution

https://youtu.be/bDHtM1wijbY [Video covers all day 1 problems]