Which statement is CORRECT about Euclid's fifth postulate?

Class 9Introduction to Euclid's GeometryGeometry — Foundations

AIt is the longest and least obvious of the five postulates.
BIt is the shortest of the five postulates.
CIt was proved from the other four postulates.
DIt is identical to the first postulate.

Step-by-Step Solution

Postulate 5 is far longer and less self-evident than the other four, which is why mathematicians tried (and failed) for centuries to derive it.

Answer: A) It is the longest and least obvious of the five postulates.

Key idea: The five postulates of Euclid

**Postulate 1**: A straight line may be drawn from any one point to any other point.

**Postulate 2**: A terminated line (segment) can be produced indefinitely (extended).

**Postulate 3**: A circle can be drawn with any centre and any radius.

**Postulate 4**: All right angles are equal to one another.

**Postulate 5** (the famous one): If a straight line falling on two straight lines makes the interior angles on the same side together less than two right angles (180°), then the two lines, if produced indefinitely, meet on that side on which the angles are less than two right angles.

These 5 statements are the seeds. Everything else in classical geometry grows from them.

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