Question

A railway passenger countsthe telegraph posts on the line as he passes them. If they are 50 
metres apart and the train is going at 48 km per hour, how many posts 
will he cross per minute? 

Answer 1

Speed per minute = 48,000 /60 = 800 meters / minute

in 800 meters there are 800/50 = 16 telegraph posts.

So the passenger crosses 16 telegraph posts each minute.  Including the first post at the beginning at t=0 minutes, the total count is 17.

After 1 minute, he crosses 17 posts.
after 2 minutes, he crosses 33 posts.
after n minutes , he crosses 16*n + 1 posts.

Answer 2

speed =- 48 km per hour

distance in metres = 48000 m

distance travelled in 1 minute = 48000/60

= 800 metre

number of telegraph posts seen = 800/50

= 16 posts.

the passenger had seen a telegraph post at the very beginning .

so total posts seen = 16 + 1 =>17 telegraph posts.