Question

A car starts from a and another point starts from point b if they travel in the same direction they meet each other in 7hrs if they meet in opposite directionvin 1hr find the streets of the car

Answer 1

Let the speed of car A be x and that of car B be y.
When they are travelling in the same direction,
Relative speed
    x + y = 7     --(1)
When they are travelling in opposite directions,
Relative speed
    x - y = 1       --(2)

Adding eqns (1) and (2), we get
   x + y = 7
   x - y = 1
__________
  2x = 8
⇒ x = 4

Now, from eqn (1), 
 4 + y = 7
⇒ y = 3

Hence, the speeds are 4 unit/hr and 3 unit/hr.