What caused plagues? filthy conditions streets water animals

ANSWER:

Animals causes plagues.

EXPLANATION:

Plague is a serious infectious disease caused by a type of bacterium named Yersinia pestis. These bacteria are usually found in rats, rodents and other mammals. In humans, it is transmitted through fleas. It is also known as Black Plague or Black death, as it can kill a person affected by it, if not treated carefully. There are 3 forms of plague, in which "bubonic plague" is the most common and dangerous one.

I'm pretty sure there's a geometry rule for   anyways, if the triangle is equilateral, and the circle is circumscribed, the circle is outside of the triangle.  to find the area, you need the radius.  the radius should be a straight line from the center of the triangle to any of it's points.  draw lines from the center of the circle to each of the triangle points.  draw three more lines from the center to the middle of the sides of the triangle.  you should now have six separate 30-60-90 triangles inside of your original triangle. use your 30-60-90 rules to solve for the radius, then the circumference. 

The answer is it can create volcanoes .