Speed of train is 55 km/hr. The length of train is 800 metre. In how much time can it cross a 1400 metre long platform?

Correct option is D

Given:

Length of train = 800 m
Speed of train = 55 km/h
Length of platform = 1400 m
Formula Used:
Speed = (Length of train + Length of platform)/Time
Solution:
​$$\text{Speed} = \frac{\text{Length of Train} + \text{Length of Platform}}{\text{Time}} \\\ \\\text{Speed} = \frac{800 + 1400}{\text{Time}} \\\ \\\Rightarrow \frac{55 \times \frac{5}{18}}{1} = \frac{2200}{\text{Time}} \\\ \\\Rightarrow \text{Time} = \frac{2200 \times 18}{55 \times 5} \\\ \\\Rightarrow \text{Time} = \frac{39600}{275} \\\ \\\Rightarrow \text{Time} = 144 \ \text{seconds}$$​​