Solution:

S: It takes X minutes to make a phone call.

Then: it takes 6 times to notify 50 people, that is:

When one person knows, he calls the second person. At this time, * * * two people know.

Two people didn't call each other, at this time * * * four people know.

Four people don't call their respective notice, at this time * * * eight people all know.

Eight people don't call their respective notice, at this time * * * sixteen people know.

16 people called each other separately, and at this time * * * 32 people knew.

At this time, there are still 18 people who don't know. Let the known 18 people inform again.

So it takes at least 6x minutes to notify everyone.

Extended data:

Reasoning and judgment: the process of reasoning and judging some phenomena in life by using tables and exclusion methods, and can express the process and results in an orderly manner.

Question type of judgment and reasoning: The first question type: graphic reasoning. One or two sets of figures are given for each question, and candidates are required to find out the law of figure arrangement through observation and analysis, and choose the one that conforms to the law.

The second question type: definition judgment. First, give a definition of each question, and then list four situations respectively, requiring candidates to choose answers that meet or do not meet the definition in strict accordance with the definition.

The third question type: analogical reasoning. Given a group of related words, it is required to find a group of words with the closest or similar logical relationship from the alternative answers through observation and analysis.

The fourth question type: logical judgment. Give a statement for each question. The hypothesis is correct and beyond doubt. Candidates are required to choose the most appropriate answer according to this statement, which should be consistent with the given statement and can be directly deduced from the statement without any additional explanation.