Question

(c) What is the time difference between Mumbai (72°54' E) and Kolkata (88° 24' E). If it is 12 noon at Kolkata, what will be the time at Mumbai?​

Answer 1

Actually there is no time difference between Mumbai and Kolkata as per Indian Standard Time.

We know that,

• Greenwich Mean Time marks the starting point of every time zone in the World and longitude passing through respective country are used for representation of time. India adopted 82°30'E as standard meridian. The time at this meridian calculated with respect to GMT is called Indian Standard Time. The time difference between GMT & IST is 5.30 Hours.
• The Sun rises from east and sets in the west. This apparent movement is caused by rotation of earth from west to east. Kolkata is on East side and Mumbai is on West side. So only we know that Sun rises early in the Kolkata than Mumbai.

Let's calculate actual time difference.

Take the case of Mumbai (72°54'E) & Kolkata (88°24'E). Each 1° longitude covered in 4 minutes.

So longitudinal difference between two cities are (88°24' - 72°54 = 15°30').

Hence actual time difference between Mumbai & Kolkata is (15°30'X4) = 62 minutes

• This means that in reality, Sun rises 62 minutes later at Mumbai than Kolkata.