When it's 10:15 in New York, it's 9:15 in Salt Lake City, and 7:15 in San Francisco - isn't it? This consistent and orderly time system, based on a grid of time zones, seems so natural that people rarely give it a moment's thought. So you may find it surprising to learn that prior to the late 1800s each community established its own time - by looking at the sun. When the sun shone directly overhead in Washington, D.C., for example, it was 12:00 noon there; up the road in Philadelphia, however, it was 12:07, and in Boston it was 12:24. To measure time with   accuracy, it is necessary to move the clock about one minute for every twelve miles of distance; so according to "sun time" your pocket watch would be slightly incorrect if you ventured only a few miles down the road. It was not until the advent of widespread railroad travel that a need arose for regularized time. At one point over 300 local times were honored within the country, making it literally impossible for trains to arrive consistently on time everywhere. As a result, in 1883 the continental, United States was divided into four time longitude. The standardization resulting from this system proved so helpful that in 1884 the International Meridian Conference applied the same procedure to establish time zones around the world. Thus, if it is 11:07 p.m. in Tuscaloosa, Alabama, a little simple research will quickly determine that in Kuala Lumpur, Malaysia, it is 9:07 A.M. - and not 9:15. The distance between Washington, D.C., and Philadelphia must be_.
more than 75 miles more than 150 miles more than 200 miles more than 300 miles