Maths Olympiad Prep

Track / Stage 3 / 86 of 260 #86 of 1964

Problem 86

AMC 10/12, early questions
Combinatorics Difficulty 3.2 Find the answer

In a "micro-video exhibition" event organized by an art group, the group will evaluate the videos from two perspectives: "likes" and "expert scores". If video A has at least one of these metrics higher than video B, then video A is considered not inferior to video B. Among the 5 micro-videos displayed, if a video is not inferior to the other 4, it is considered an excellent video. What is the maximum possible number of excellent videos among these 5?

A number or a short expression. Spacing, $ signs and \frac vs / are all fine.

Official solution

Let's denote the 5 micro-videos as A1_{1}-A5_{5}. We start by considering a scenario with only 2 videos, A1_{1} and A2_{2}:

- If the number of likes for A1_{1} > the number of likes for A2_{2}, and
- The expert score for A2_{2} > the expert score for A1_{1},
then we can have at most 2 excellent videos.

Next, we consider a scenario with 3 videos, A1_{1}, A2_{2}, and A3_{3}:

- If the number of likes for A1_{1} > the number of likes for A2_{2} > the number of likes for A3_{3}, and
- The expert score for A3_{3} > the expert score for A2_{2} > the expert score for A1_{1},
then we can have at most 3 excellent videos.

By extending this pattern, we can infer that among these 5 micro-videos, we can have at most 5 excellent videos.

So, the answer is: 5\boxed{5}.

This problem tests our understanding of basic logical reasoning, making it a fundamental question.

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.