Difference between revisions of "2023 IMO Problems/Problem 5"

(Solution)
(Solution)
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==Solution==
 
==Solution==
 
<math>k=\lfloor\log_2(n)\rfloor+1</math>
 
<math>k=\lfloor\log_2(n)\rfloor+1</math>
 +
 
https://www.youtube.com/watch?v=jZNIpapyGJQ [Video contains solutions to all day 2 problems]
 
https://www.youtube.com/watch?v=jZNIpapyGJQ [Video contains solutions to all day 2 problems]
  

Revision as of 16:38, 30 April 2024

Problem

Let $n$ be a positive integer. A Japanese triangle consists of $1 + 2 + \dots + n$ circles arranged in an equilateral triangular shape such that for each $i = 1$, $2$, $\dots$, $n$, the $i^{th}$ row contains exactly $i$ circles, exactly one of which is coloured red. A ninja path in a Japanese triangle is a sequence of $n$ circles obtained by starting in the top row, then repeatedly going from a circle to one of the two circles immediately below it and finishing in the bottom row. Here is an example of a Japanese triangle with $n = 6$, along with a ninja path in that triangle containing two red circles.

[Image to be inserted; also available in solution video]

Solution

$k=\lfloor\log_2(n)\rfloor+1$

https://www.youtube.com/watch?v=jZNIpapyGJQ [Video contains solutions to all day 2 problems]

See Also

2023 IMO (Problems) • Resources
Preceded by
Problem 4
1 2 3 4 5 6 Followed by
Problem 6
All IMO Problems and Solutions