# Constants

Constants are quantities that do not change. They're like crotchety old curmudgeons, forever stuck in their ways.

• 3, 57, 299, and  are constants.
• π and e are also constants.

We can also use letters to represent unknown constant values.

### Sample Problem

Joey gets d dollars for each odd job he does for his grandpa. His grandpa literally told him he would pay him d dollars for each job, probably so that old coot could stiff his grandson when it came time to tell him how much d is. No matter what the job is, Joey is paid the same. If Joey does t odd jobs for his Grandpa in a day, how much money does Joey make that day?

We don't have any amounts, and therefore, we can only answer this question in terms of the variables we're given. Joey makes d · t dollars in a day, since that's his pay per job times the number of jobs he does. Because Joey gets paid the same amount per job, d will never change; therefore, we call it a constant. The varying quantity in this problem is t, since the number of jobs Joey does per day will vary depending on what his grandpa forces—pardon us—asks him to do.