Hi, first post, as I'm at a total loss with this. I'm sure I'm missing something obvious but can't get my head round it. Hopefully someone here will.

We have an unknown number between 1 and 999, which we'll call x

x falls midway within a range of 100

I am allowed to make a guess at x, after which I get an indication of how close I am ranging from -3 through to +3 including 0. If my feedback is zero, I am within the range of 100.

I need to work out a formula, to calculate my next guess, to calculate one edge of the range in as few attempts as possible. eg guess = 341, feedback = +1. Guess 340, feedback = 0.

I think this revolves around some sort of iteration formula, but am needing help on this one.

Many Thanks