A train running at a speed of 90 km/hr crosses a platform double its length in 36 seconds. What is the length of the platform in meters?

1200
2300
3450
4None of these

Answer:- 1

Explanation:-

Solution:

\begin{aligned} Let the length of the train be x metres . \\ Then, length of the platform  =  (2 x) metres . \\ Speed of the train \\ = (90 \times \frac{5}{18}) m / \sec \\ = 25 m / s e c \\ ∴ \frac{x + 2 x}{25} = 36 \\ \Rightarrow 3 x = 900 \\ \Rightarrow x = 300 \\ Hence, length of platform \\ = 2 x = (2 \times 300) m = 600 m \end{aligned}

$\eqalign{ & {\text{Let the length of the train be x metres}}{\text{.}} \cr & {\text{Then, length of the platform = (2}}x{\text{) metres}}{\text{.}} \cr & {\text{Speed of the train}} \cr & {\text{ = }}\left( {90 \times \frac{5}{{18}}} \right)m/\sec \cr & = 25m/sec \cr & \therefore \frac{{x + 2x}}{{25}} = 36 \cr & \Rightarrow 3x = 900 \cr & \Rightarrow x = 300 \cr & {\text{Hence, length of platform}} \cr & {\text{ = }}2x = \left( {2 \times 300} \right){\text{m}} = 600{\text{m}} \cr}$