Anne King, age 10, of Orleans, Ontario, Canada, for her question:

Where is the exact center of North America?

Earth scientists call this spot the geographic center of North America. If the continent were a perfect circle of land, it would be fairly easy to find the exact center. But North America is not a neat circle. Neither is any other land on earth. So finding the geographic center calls for lots of exact measuring in all directions, plus a bit of pretending. Let's pretend that the lakes and inland waters are dry land and that the land measures the same distance in all directins. Let's include the offshore islands that rightfully belong to the continent. This map, of course, is impossible. But the idea makes it easy to pinpoint the geographic center of the continent.

North America, of course, includes all of Canada and Mexico, Alaska and 48 other states of the United States. Its total area is 9,416,000 square miles. And its geographic center is in the northern region of the state of North Dakota. This lovely region of lakes and forested slopes is near the center of Pierce County. Here, just southwest of the town of Rugby, stands a stone monument that marks the exact geographic center of North America    which is the third largest of the world's seven continents.