Correct option is (b) 60 km/hr
Let the speed of train be x km \hr
Relative speed = (30 + x) \(\times \frac 5{15}\)
\(= \frac{150 + 5x}{18}\) km sec
\(\therefore \frac{150 + 100}{\frac{150 + 5x}{18}} = 10\)
⇒ 18 × 250 = 10(150 + 5x)
⇒ 4500 =1500 + 5x
⇒ 5x = 4500 − 1500
⇒ 5x = 3000
⇒ x = 60km/hr