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Question

Difficulty: EasyLatitude, Longitude, and Time Calculations

City A is situated at longitude 15∘E15^\circ\text{E} where the local time is 1:00 PM. What is the local time at City B, located at longitude 60∘E60^\circ\text{E}?

  1. A
    10:00 AM
  2. B
    2:00 PM
  3. 4:00 PMAnswer
  4. D
    5:00 PM

Answer

4:00 PM
The difference in longitude between 15∘E15^\circ\text{E} and 60∘E60^\circ\text{E} is 45∘45^\circ. Since 15∘15^\circ of longitude corresponds to 1 hour of time difference, 45∘45^\circ equals 3 hours (45÷15=345 \div 15 = 3). Because City B lies further east than City A, time is ahead. Adding 3 hours to 1:00 PM yields 4:00 PM.

Step-by-Step Solution

1
Calculate the difference in longitude between the two locations
60∘E−15∘E=45∘60^\circ\text{E} - 15^\circ\text{E} = 45^\circ
Both locations are in the Eastern Hemisphere, so subtract the smaller longitude from the larger longitude.
2
Convert the angular difference into time difference
45∘÷15∘ per hour=3 hours45^\circ \div 15^\circ\text{ per hour} = 3\text{ hours}
The Earth rotates 15∘15^\circ in 1 hour (360∘360^\circ in 24 hours).
3
Adjust local time based on direction of movement
1:00 PM +3 hours=4:00 PM+ 3\text{ hours} = 4:00\text{ PM}
Eastward movement results in time gain (East-Gain, West-Loss), so add the time difference to the known time.

Key Concept

Longitude and Time Difference Calculation
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Topics

Latitude, Longitude, and Time Calculations

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