Mathematical model is this system of 2 equations for 2 unknowns x + y = 210,+ = 6. where x is the distance the driver covered at the speed of 60 mph, y is the distance covered at the reduced speed of 10 mph. The system is consisted and x = 180 mi, y = 30 mi is one possible solution. Hence, this solution is unique. The problem is solved.
Let distance at reduced speed (10 mph) be D
Then distance traveled at 60 mph = 210 – D
Time traveled at 10 mph:
Time traveled at 60 mph:
We then get:
6D + 210 – D = 360 --------- Multiplying by LCD, 60
6D – D = 360 – 210
5D = 150
D, or distance covered at reduced speed (10 mph) =, or miles