But as you, though inadvertently and without intending so unreasonable a question, asked me 'what for?'

I suddenly feel a little sorry for him: it was not, after all, an unreasonable question.

It wasn't an unreasonable question, Heikki thought, irritably, but said nothing.

"I don't think it's an unreasonable question, given who we both are," Eric responded.

While you could say on one hand that's kind of an unreasonable question, on the other hand, is it really?

Which, when you thought about it, wasn't such an unreasonable question.

It wasn't an unreasonable question, just out of place, like asking about casket expenses during a funeral.

It is not an unreasonable question to ask.

These are not unreasonable questions which I feel perfectly happy to answer over the next few days.

Not an unreasonable question, even if a bit crudely put.