(b) 60 km/hr
Let the speed of the second train = x km/hr
Since both the trains are running in opposite directions. Their relative speed = (30 + \(x\)) km/hr = (30 + \(x\)) x \(\frac{5}{18}\) m/sec
∴ Time taken to pass another train = \(\frac{\text{Sum of the lengths of both the trains in metres}}{\text{Relative speed in m/sec}}\)
⇒ 10 = \(\frac{(150+100)}{(30+x)\times\frac{5}{18}}\)
⇒ (30 + \(x\)) = \(\frac{250\times18}{10\times5}\) = 90
⇒ \(x\) = (90 – 30) km/hr = 60 km/hr.
