Brainliest!

A 450 m long freight train passes through a tunnel at a speed of 20 m/sec.

On the return journey it takes 45 sec longer for the train to pass completely

through the same tunnel when it travels at a lower speed of 15 m/sec. How

long is the tunnel?

Speed=Distance/TimeSo Distance=Speed*TimeTherefore we have L(Lenght of the tunnel)=V1 * t1 = V2 * t2There is a 45sec difference between t1 and t2, in other words t2-t1=45sec => t2= t1+45 (t2>t1 because it takes more time at a lower speed; V1>V2 => L/t1 > L/t2 => 1/t1 > 1/t2 => t1<t2: t1-t2=45 is not possible )So V1* t1 = V2* (t1+45) => t1 * (V1-V2)=V2 * 45 => t1= (V2* 45)/(V1-V2)= (15*45)/(20-15)=135m