a) 10 km/hr
b) 18 km/hrs
c) 72 km/hr
d) 36 km/hr
Answer: d
Explanation: Let the speed of each train be x m/sec.
Then, relative speed of the two trains = 2x m/sec
So, 2x = $$\frac{{120 + 120}}{{12}}$$
2x = 20
x = 10
Speed of each train = 10 m/sec
= $$\left( {10 \times \frac{{18}}{5}} \right)$$ km/hr
= 36 km/hr
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