Question

two cars are 100 miles apart.if. if they drive towards each other they will meet in 1 hour .if they drive in the same direction they will meet in 2 hours.find their speed by using graphical method.

Answer 1

Let speed of first Car = x mile/h

and speed of 2nd car = y mile/h

distance between two cars = 100 miles

a/c to question,
if they drive towards each other they will meet in 1 hour .

so, distance/relative speed of cars = time,

[ if two car approach each other then, relative speed of first with respect to 2nd = sum of speed of cars ]

or, 100 /(x + y) = 1

or, x + y = 100 ..........(1)


again, if they drive in same direction they will meet in 2 hours .

so, distance/relation speed of cars = time,

[ if two objects moves in same direction then, relative speed of Frist with respect to other is difference of their speed ]

so, 100/(x - y) = 2

or, x - y = 50 ...........(2)

see graph, equations (1) and (2) intersects at (75, 25)

hence, speed of first car = 75 mile/h

speed of 2nd car = 25 mile/h