A math teacher dove by a playground that was full of boys and dogs the teacher happened to notice that there was a total of 40 heads and 100 feet how many boys and how many dogs were there?

I think that there were 40 boys and dogs since there were forty heads but, I'm not sure because the feet part kinda confuses me. The answer would be 40 boys and 5 dogs (but dogs don't technically have feet, they have paws?) If you saw 40 heads, you wouldn't be able to see the dogs head, unless they were as tall as the boys? No your over thinking it. It's 30 kids and 10 dogs = 40 heads. Then 30 x2=60 and 10x4=40 so 60+40= 100 legs