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Modern Arithmetic III, Article 82

To complete this lesson, complete the following tasks:

1.   Study the lesson for mastery.
2.  Memorize the lesson that it may be recited.
3.  Complete the lesson assessment.

Lesson

1.  When is it “noon” (12 o’clock) at any place?
It is noon (12 o’clock), at any place when the sun is on the meridian of that place.

2.  How does the movement of the sun affect the time in different places?
As the sun appears to travel from the east toward the west, when it is noon at any place, it is after noon east of that place, and before noon west of that place.

3.  What causes a place to have later or earlier time than another place?
A place has later or earlier time than another, according as it is east or west of it.

4.  What is the rule for finding the time of different places?
Therefore, when the time at one place is given, the time at another, if EAST of this, is found by adding their difference of time; if WEST, by SUBTRACTING their difference of time.

Self-Assessment

Note:  For the exercises below, you may need to look back to the information provided in article 81.  Work until you are able to reach the correct answers below.  If you are unable to do so, contact us for help.

1. When it is noon at Cincinnati, what is the time at Philadelphia?
2. When it is 11 o’clock A. M. at New York, what is the time in longitude 30° east of New York?
3. When 12 o’clock (noon) at Philadelphia, what is the time at Cincinnati?
4. When it is 11 o’clock A. M. at New York, what is the time at St. Louis?
5. Wheeling, W. Ya., is in longitude 80° 42′ west: the mouth of the Columbia river, in longitude 124° west: when it is 1 o’clock P. M. at Wheeling, what is the time
at the mouth of Columbia river?

Answers:
1.  37 min. 20 sec. past noon.
2.  1 P. M.
3.  11 hr. 22 min. 40 sec. A. M.
4.  9 hr. 55 min. 4 sec. A. M.
5.  10 hr. 6 min. 48 sec. A. M.