GIVEN: (i) Speed (S) = 180 kmph (ii) Time to cross tree (T) = 9 sec. FORMULA USED: (i) Distance (Length of train) = (Speed × Time) CALCULATIONS: Let, convert speed and time in same unit Speed = 180 × (5 ÷ 18) m/sec = 50 m/sec Length of the train (L) = (speed × time) ⇒ L = 50 × 9 ∴ L = 450 meter ∴ Hence, Length of train is 450 meter.