A train runs past a telegraph pole in 15 s and through a tunnel of length 450 m in 45 s. The length of the train is

Let the speed of train = v

To cross a telegraph pole s = Length of train.

Time taken t = 15s

So $\text{v}=\frac{\text{s}}{\text{t}}=\frac{\text{s}}{\text{15}}$

To cross a tunnel of length 450m

Distance travelled ${\text{s}}^{\text{|}}=450+\text{s}$

Time taken ${\text{t}}_{\text{2}}=45\text{s}$

So $\text{v}=\frac{{\text{s}}^{\text{|}}}{{\text{t}}_{\text{2}}}=\frac{450+\text{s}}{45}$

We get

$\frac{\text{s}}{15}=\frac{\text{s}+\text{450}}{45}$

$\text{3s}=\text{s}+450$

$\text{3s}-\text{s}=450$

$\text{s}=\frac{450}{2}=225$

$\text{s}=225\text{m}$