Question

points A and B are 70km a part on a highway,a car starts from A and another car starts from B simultaneously. if they travel in the same direction, they meet in 7 hours, but if they travel towards each other, they meet in one hour.find the speed of two cars

Answer 1

let speed of A be x.
     speed of B be y.
relative speed of A and B in same direction is given by x-y.
relative speed of A and B in opposite direction is given by x+y.

therefore
70=(x-y)7........x-y=10......equ1.
70=(x+y)1.......x+y=70.....equ2.

sloving 1 and 2 

x=40 , y=30

therefore

speed of A is 40 km/hr.
speed of B is 30 km/hr.