Calculate speed of the first train

Since the first train passes a pole, the distance covered is its own length. $V_1 = \frac{180}{12} = 15$ m/s.

$V_1 = 15 \text{ m/s}$

Calculate relative speed during overtaking

When the second train overtakes the first, the total distance covered is the sum of their lengths: $180 + 120 = 300$ m. $V_{rel} = \frac{300}{15} = 20$ m/s.

$V_{rel} = \frac{300}{15} = 20 \text{ m/s}$

Calculate speed of the second train

In the same direction, $V_{rel} = V_2 - V_1$ (assuming $V_2 > V_1$). So, $V_2 = 20 + 15 = 35$ m/s.

$V_2 = 35 \text{ m/s}$

Convert speed to km/h

Convert m/s to km/h by multiplying by $\frac{18}{5}$: $35 \times \frac{18}{5} = 7 \times 18 = 126$ km/h.

$V_2 = 35 \times \frac{18}{5} = 126 \text{ km/h}$