Difference between revisions of "2020 IMO Problems/Problem 3"

 
(One intermediate revision by the same user not shown)
Line 1: Line 1:
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]
 +
 +
==See Also==
 +
 +
{{IMO box|year=2020|num-b=2|num-a=4}}
 +
 +
[[Category:Olympiad Combinatorics Problems]]

Latest revision as of 10:31, 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]

See Also

2020 IMO (Problems) • Resources
Preceded by
Problem 2
1 2 3 4 5 6 Followed by
Problem 4
All IMO Problems and Solutions