On a cold day (0C) you observe a person far away from you hit a piece of metal with a hammer. Then 0.75 seconds later you hear the sound of the hammer hitting the metal. How far are you from the other person?

248.48 meters

Explanation:

When there is low temperature than the normal room temperature, the speed of sound in air decreases because at lower temperatures the movement of air molecules through which the sound travels gets decreases.

Speed of sound at 0⁰ is found to be approximately 331.3 m/s.

The question says that sound was heard by the observer 0.75 seconds later after hammer hit the metal.

As we know, Distance traveled = Speed × Time taken

So, distance traveled by sound in 0.75 seconds = 331.3 × 0.75 = 248.48 m

So, the observer was standing 248.48 meters away from the other person hitting the hammer.

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.