Atrain 375 m long is running at a speed of 45 km/hr. how long will it take to pass a single post

we know that

The time it takes for the train to pass a single post is equal to the time it takes for the train to pass its length.

the length of the train is-----> 375 m

convert to Km

1 Km =1,000 m

375 m=375/1,000=0.375 Km

the speed of the train is 45 km/hour

so

by proportion

convert to minutes

1 hour=60 minutes

0.0083 hours=0.0083*60=0.5 minutes

convert to seconds

1 minute=60 sec

0.5 minutes=0.5*60=30 sec

therefore

the answer is

30 seconds