Question 271780
the formula for direct variation is y = k*x


let y = the pressure.
let x = the depth.


you get:


21 = k*50


this makes k = 21/50 = .42


your constant of variation is .42


at 0 depth, the pressure should be 0.


based on this formula, the pressure at 0 feet is equal to:


y = 0*.42 = 0


this would be additional pressure over the normal pressure of the atmosphere.


at 10 feet, the pressure would be:


y = 10*.42 = 4.2 pounds per square inch.


at 50 feet, the pressure would be:


y = 50 * .42 = 21 pounds per square inch.


at 100 feet, the pressure would be:


y = 100 * .42 = 42 pounds per square inch.


you can see that as x gets greater, y gets greater which means they are directly proportional.


here's some additional information on variation for you.


<a href = "http://www.purplemath.com/modules/variatn.htm" target = "_blank">http://www.purplemath.com/modules/variatn.htm</a>