Now, just as we did earlier, we complete our formula with the pertinent figures. P1, the proportionate distance for the south half mile, is to the record distance as the retracement total is to the record total, or P divided by 40 equals 79.30 divided by 79.50.

Shift the 40 to the other side and P1 equals 40 times 79.30 divided by 79.50 or 39.89937 which rounds out to 39.90.

This would be our proportionate distance for the south half mile, North 39.90 chains.