The correct option is B 80 km
Given,
Speed of the train = 120 km/hr
i.e., in 60 minutes, it covers 120 km.
For the same speed, more the time, more distance will be covered.
So, Time(x)∝Distance(y)
∴ x1y1 = x2y2
Given,
x1 = 60 mins
y1 = 120 km
x2 = 40 mins
and y2 = distance covered in 40 mins
⇒ 60120 = 40y2
⇒y2 = 40 × 12060 = 80 km