It takes 19 seconds for a train to pass a 450 meter long bridge and 30 seconds to pass a 780 meter long tunnel at the same speed

It takes 19 seconds for a train to pass a 450 meter long bridge and 30 seconds to pass a 780 meter long tunnel at the same speed

Train speed: (780-450) / (30-19) = 30 m / S
Train length: 30 * 19-450 = 120m

It takes 19 seconds for a train to pass a 450 meter long bridge and 30 seconds to pass a 780 meter long tunnel at the same speed
Don't use equations, use formulas, and talk about ideas

It takes 24 seconds for a train to pass through the first 375 meter long tunnel, and then 16 seconds to pass through the second 231 meter long tunnel

Let the length of the train be x meters, then the speed of the false train remains unchanged, then there is an equation
(375+X)/24=(231+X)/16
The solution is x = 57