When trying to solve a problem, you may run into a situation with 2 variables. At first you may feel stumped. But just take a breath and ask yourself: “Is this a situation where one of the variables may be redefined by some factor of the other variable?”
What does this mean?
a situation with 2 variables
Well consider the following problem.
24 vehicles pass by a traffic monitor. Some of the vehicles are motorcycles and some of them are 4 wheeled vehicles.
There were 80 wheels in all.
How many 4 wheeled vehicles went by?
When first thinking this through one realizes that there are 2 variables to this problem.
X is for motorcycle with 2 wheels and Y is for a vehicle with 4 wheels.
2X + 4Y = 80
But are there really 2 variables? In terms of wheels you could say that Y is equal 2x.
y = 2X
2X + 4(2X) = 80
Then solve for X.
2X + 4(2X) = 80
2x + 8x = 80
10X = 80
X = 8
Now since you know Y = 2X, solving for Y is easy.
y = 2X
y = 2(8)
y = 16
By this you cans see that 16 vehicles with 4 wheels went by.
When faced with multiple variables, see if it is possible to redefine variables in terms of another variable.