According to the station clocks, two babies are born at the same instant, one in Howrah and other in Delhi. (a) Who is elder in the frame of 2301 up Rajdhani Experess going from Howrah to Delhi? (b) Who is elder in the frame of 2302 Dn Rajdahni Express going from Delhi to Howrah .

Explanation

The birth timings recorded by the station clocks is the proper time interval because it is the ground frame .That of the train is improper .
I.e. ` Delta T' = v Delta T `
Hence for (a) up train Delhi baby is elder (b) down train Howrah baby is elder .