Question

A train cross a bridge and platform of lengths 450m and 700m in 20sec and 30 sec respectively.find the speed of train

Answer 1

22.9999m/s

t1=20;     d1=450m

t2=30;  d2=700m

s1=d1/t1;    s2=d2/t2;

s1=22.5;    s2=23.99999999

s=(s1+s2)/2

s=22.999999m/s

Answer 2

Step-by-step explanation:

Given: $T1= 20 second, T2=30 second$ and length of platforms is $450m$ and $700m$

To find: Speed of train

We know that the formula of speed is $s=\frac{d}{t}$

i.For calculation of speed 1,

We know that T1$=20$ and D1$=450$

⇒ $S1= \frac{450}{20}$

⇒ $S1= \frac{45}{2} = 22.5$

ii. For calculation of Speed 2,

We know that T2$= 30$ and D2$= 700$

⇒ $S2= \frac{700}{30}$

⇒ $S2=\frac{70}{3}= 23.9$

For calculation of speed of the train,

We know that total Speed $= \frac{S1+S2}{2}$

⇒ $S=\frac{22.5+23.9}{2}$

⇒ $S= \frac{46.4}{2}$

⇒ $S=23.2 m/s$

The speed of the train is $23.2m/s$.