Given that,
Velocity of train = 100 km/hr
Velocity of another train = 50 Km/hr
We need to calculate the relative velocity of second train with respect to the first train
Using formula of relative velocity
\(V_{AB} = \sqrt {(OA)^2 + (OB)^2}\)
Put the value into the formula
\(V_{AB} = \sqrt {100^2 + 50 ^2}\)
\(V_{AB} =111.80\,km/h\)
Hence, The relative velocity of second train with respect to the first train is 111.80 km/hr.