As the height above earth increases, what happens to the number of particles of gas in the atmosphere?

Which of there factors contributed most to us westward expansion in the second half of the nineteenth century?

Geologists know that potassium-40 decays to argon-40, with a half-life of 1.3 billion years. if an analysis of a feldspar crystal in a sample of granite shows that 75 percent of the potassium-40 atoms have decayed to form argon-40, what is the age of the granite

In a constitutional monarchy, the king or queen a. is a symbol of the nation b. runs for office c. controls the legislative branch d. has absolute control