# If it is 12 noon and prime meridian, then calculate the time 75° east and 50° west longitudes.

Since the earth makes one complete revolution of 360° in 24 hours.

Earth rotates 360 ° in 24 hr.

Then in 1 hr =360°/24=15°

1 hr=15°

Also, 1 hr = 60 min.

15°= 60min.

1° = 60/15

So, 1°= 4min.

As you must know that Earth rotates from west to east, so every 15° we go eastwards local time is advanced by 1 hour.

In the same way, if you go westwards, local time is retarded by 1 hour.

75° toward the east

According to the above explanation, now you know that the Earth takes 1hour to rotate 15°.

Therefore, if we divide 75° in an equal part of 15° then the equal part comes is 5.

15° + 15° + 15° + 15° + 15° = 5 hour (15° = 1hour) ahead as we are moving towards the east.

12 + 5hr = 5:00 p.m

Hence, time in 75° east it will be 5:00 p.m

Now, 50° toward the west

We divide 50° into 3 parts of 15° each and we multiply 4 in the remaining 5° as we know 1° longitude means 4 minutes.

15°+15°+ 15°+ (5°×4=20min)= 3 hours 20 minutes behind as we are moving towards the west.

12 – 3 hours 20 minutes = 8:40 a.m

Hence, time in 50° west it will be 8:40 a.m

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Updated on: 10-Oct-2022

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