Let a child enjoy a correct answer before asking why it took so long.

Getting there matters more than the speed of getting there, but the adult question about the delay tends to arrive first and land on top of the success. What the child hears is that being right was not quite enough. Over time that makes effort anxious, and they begin guessing at answers rather than working toward them.

Let the correct answer have its moment with nothing attached. If speed genuinely matters, teach it later as its own separate skill. The pleasure of getting something right is the fuel for the next attempt.