There are 4 workers taking turns looking after 4 kids. So while at any given time 1 worker is looking after 4 kids, you need 4 workers to cover all the shifts. Thus one-to-one
That's a very odd framing. So it works out to one worker per one shift/day? Wouldn't that be true if there were 10 or 20 kids yet still 1 worker per shift?
