A train $280m$ long is moving at a speed of $60km/hr$. What is the time taken by it to cross a platform $220m$ long?

Time taken:

Length of the train $=$$280m$

Length of the platform $=$ $220m$

Hence, to cross the platform completely the train has to cover a distance of

$$\begin{gathered} \mathrm{Distance}\mathrm{covered}=\mathrm{length}\mathrm{of}\mathrm{train}+\mathrm{length}\mathrm{of}\mathrm{platform} \\ \mathrm{Distance}\mathrm{covered}=280+220\mathrm{m}=500\mathrm{m} \\ \mathrm{Distance}\mathrm{covered}=\frac{500}{1000}\mathrm{km}=0.5\mathrm{km} \end{gathered}$$

Hence, we can find the time as when speed and distance covered is given we use the formula:

$$\begin{gathered} \mathrm{Time}\mathrm{taken}=\frac{\mathrm{distance}\mathrm{covered}}{\mathrm{speed}} \\ \mathrm{Time}\mathrm{taken}=\frac{0.5}{60}\mathrm{hr}=\frac{0.5}{60}\times 60\min =0.5\min \\ \mathrm{Time}\mathrm{taken}=0.5\times 60\sec =30\sec \end{gathered}$$

Therefore, he time taken by it to cross a platform $220m$ long is $30seconds$.