Interviewers can only respond to what you say, and poor communication, like in this example, not only wastes time, but is a poor reflection on your candidacy. This is a crucial point to remember. No matter how brilliant you may be, if you cannot communicate that brilliance, and do so in a manner laymen would understand, your intellect counts for little in a case interview since it is all about demonstrated competency. You must demonstrate your competency. Period.