S27 — Counting what is left after something did the removing

Albino alligators hatch in the swamp and in the zoo at the same rate. You only ever see them in the zoo. Walk the swamp and count: about one white alligator in every thousand. Now work out how many hatched that way.

Predict first. A white hatchling does worse in the swamp than a normal one. You walk the swamp and find one white alligator in every thousand. The number that hatched white, per thousand, is:

Set the swamp

1
1.00×
white alligators you would find, per thousand:
Find three different hatch rates that all leave about one white per thousand in the swamp. 0/3

What hatched, and what you find

Both marks are rates per thousand, on a scale where each step is ten times the one before. The gap between them is whatever did the removing.

You matched the same swamp count three different ways. From the count alone — one white per thousand found — the number that hatched white is: