Plane speed

Question

Two planes which are 2660 miles apart, fly towards each other.  Their speeds differ by 65 mph.  If they pass each other in 4 hours, what is the speed of each?

Answer 1

Let's assume the pair of unknown variables X and Y represents the speed of these two planes. The problem can be written as the following system of 2 linear equations:

 

4(X+Y)=2660

X-Y=65

 

or in canonical form:

 

4X + 4Y = 2660

X-Y= 65

 

It can be solved either manually or using online equations solver (http://examn8.com/SystemOfEquations.aspx), giving the answer: X=365 mph and Y=300 mph.