All metals are conductors — Syllogisms Aptitude Question
All metals are conductors: Statements: All metals are conductors. Copper is a metal. Conclusions: I. Answer and worked solution on CodeKairo.
- Topic: Syllogisms
- Section: Logical Reasoning
- Difficulty: Easy
- Time target: 60 seconds
Question
Statements:
- All metals are conductors.
- Copper is a metal.
Conclusions: I. Copper is a conductor. II. All conductors are metals.
Which conclusion follows?
Options
- Only I
- Only II
- Both
- Neither
Show the answer and the worked solution
Correct answer: A. Only I
Worked solution
- Copper ⊂ metals ⊂ conductors, so copper is a conductor: I follows.
- II reverses statement 1 and is invalid.
Answer: Only I.
The idea
A named individual inside a class inherits everything true of that class. Reversal remains invalid however obvious it may seem.
Shortcut. A named member inherits its class's property, so I is immediate. II is statement 1 read backwards, and an 'all' converts only to 'some' (some conductors are metals), never to 'all' — so every option containing II goes.
Common trap. "Both" — accepting II as a harmless restatement of statement 1; graphite and salt water conduct without being metals, so the reversed 'all' fails.