So if you ignore mass and just look at quantity.

1 + 1 = 1

This is borrowed from the lessons we teach our kids. For example. "If I take one apple and add another apple how many apples do I have?"......."TWO!!!"

My example "If I have one pile of sand, and I sweep another pile of sand into it, how many piles of sand do I have?"................................."one?"

Exactly