Disguised Pair Logic

Sometimes referred to as “Hidden Pair,” this is a form of what graph theorists call Pile Exclusion. A Disguised Pair happens when the only instances of two numbers are in two cells, but those cells have other occupants as well. Because one of the two numbers must reside in one of the two cells, and the other number must reside in the other cell, any other occupant is a straggler and can be erased. As an example, consider the row below. Notice that the numbers 2 and 4 only occupy the third and sixth cells, along with a few other inhabitants.

Because the 2s and 4s are only found in two cells, stragglers (numbers besides 2 and 4) can be erased from the third and sixth cells. See the simpler, resulting row below.