Apopulation has a birthrate of 10/1000 , a death rate of 9/1000, an immigration rate of 3/1000, and an emigration rate of 7/1000. what is the populations growth ?

On average, for every 1000 people in the given area/country, 10 get born (+10), 9 die (-9), 3 immigrate (+3), 7 emigrate (-7), i.e., the net total becomes -3 people per 1000. This corresponds to a percentage growth rate of -0.3%.

If I am at the station that the train is approaching, and if the train is making some kind of steady sound, then as the train draws closer, I hear the amplitude of the sound steadily increasing ... it gets louder and louder as the train gets closer and closer to me.

(The frequency of the sound I hear is higher than the frequency of the sound the train is actually making, but I don't know that, because I have no idea what frequency sound the train is actually making.)

If anybody tries to tell you that the frequency of the sound from the train keeps getting higher and higher, please tell that person to come see me, and I will straighten him out.  It doesn't.