Text version of this lesson
See the "and", "or" and "not" relationships on Venn diagrams.
Key takeaway: A Venn diagram lets you check complex logical relationships by eye.
Question 1
The left circle is people who speak English. The right circle is people who can code. Which region holds those who do both?
Show answer and explanation
Why: Right. The intersection is where both properties meet in one person.
Hint: Which region does "both ... and" point to?
Question 2
The left circle reads books, the right watches films. Mark every region that fits "reads books or watches films".
Show answer and explanation
Why: Yes. A union is everything that belongs to at least one of the sets.
Hint: In logic, "or" normally includes the both case too.
Question 3
Three circles: Python, SQL and English. Which region holds the people who have all three?
Show answer and explanation
Why: Excellent. People in the centre have Python, SQL and English all at once.
Hint: Each circle stands for one skill.
Question 4
The circle is people who cycle. Which region holds the people who do not cycle?
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Why: Right. The complement is everyone in the whole group who is not in that set.
Hint: What is the word "not" asking for?
Question 5
All backend developers can code. All NestJS developers are backend developers. Which conclusion is forced?
Options
- Everyone who can code is a NestJS developer.
- Every NestJS developer can code.
- Only NestJS developers are backend developers.
- Backend developers use nothing but NestJS.
Show answer and explanation
Answer: Every NestJS developer can code.
Why: Right. NestJS developer -> backend developer -> can code. These sets nest inside one another.
Hint: Which set contains the NestJS set?