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ICSE Class 9 Geography Question 9 of 22

Geographic Grid: Latitudes and Longitudes — Question 21

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Question

Question 21

Assertion (A): There is a time difference of a full day on crossing the IDL.

Reason (R): It is diametrically opposite the Greenwich Meridian.

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R does not explain A.
  3. A is true but R is false.
  4. A is false but R is true.
Answer

Both A and R are true and R is the correct explanation of A.

Explanation — The line of longitude 180° or IDL is one and the same for East or West of the Prime Meridian. Since it is diametrically opposite to the Greenwich Meridian it causes a time difference of a full day on crossing the line. The time difference works out to 12 hours (180° x 4 min) from either side. Thus, on crossing the line, a day is gained or lost.