Anu is taller than Bobby. Bobby is taller than Chetan

Why

Samar's caution is a genuinely good habit — often, two separate facts really do need a third piece of information to connect them. Height comparisons, though, chain together automatically: if Anu is taller than Bobby, and Bobby is taller than Chetan, then Anu must be taller than Chetan too — there is no way to arrange three heights where this fails, because 'taller than' always carries over down the line (mathematicians call this a transitive relation). Test it with real numbers: pick any heights fitting the rule, say Anu=150cm, Bobby=145cm, Chetan=140cm — Anu is automatically taller than Chetan, and no matter what specific numbers you try (as long as they fit the two given facts), Anu always ends up taller than Chetan. His sister is right: Anu is definitely taller than Chetan — height comparisons chain together on their own, unlike facts that need an extra connecting clue.