why is it important to define a variable before writing an equation?

Question

I'm in 8th grade and can't seem to figure it out. NEED ASAP 

 

Answer 1

An equation defines the relationships between the variables themselves and between the variables and other given information in the problem. If I have not yet defined specifically to what the variables reference, I cannot possibly make any statement regarding the relationships between the variables and any other quantity. 

Answer 2

it is important because you need to recognize what it is that you are solving for. 

lets say you work 20 hours, and get paid $7.50 an hour. you want to know how much you will be paid. so h, (your paycheck amount) becomes your variable. you define it, and it lets you know how to properly write the equation.

 

7.50*20= h

h/20 = 7.50

Answer 3

Skylar,

          You usually want to find the value of some unknown quantity(s) and you will be given, or otherwise discover that the unknown quantities are related to other information that is known. If you want to solve for the unknowns using mathematical equations it is necessary to define the unknown variables i.e. what they represent in the real world so that the known relationships can be expressed in equation form.

       A simple example: suppose I'm going to travel 500 miles and I think I can maintain a speed of 50 miles per hour and I want to know how long it will take me to reach my destination. In this case the variables are: speed, we'll call it s, distance traveled call it d and the trip time call it t. We have now defined our variables by giving them names and physical units. Now to find the unknown trip time t we use the known relationship d=s*t. We can now use algebra to solve for t the trip time t in terms of the known quantities d and s i.e. t=d/s=500 mi/50 mph=10 hrs which is the value of the unknown variable t. Q.E.D. :)

 

Hope this helps, if not let me know

 

Jim