Adverbs tell how, where, when, and why. Adjectives tell how much/many, which one/s, and what kind. So "when" is an adverbs and "how tall" and "how much" are adjectives.
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JumanahAre these "interrogative adverbs" or "interrogative adjectives"?These? What are "these"? I assume you mean the words "how" and "when". In your example sentences they are interrogative adverbs. "where" and "why" fall into the same category.