Distance between A and B is 420 km. When they start moving towards each other they meet in 7 hours. If A start moving 4 hours after B then they meet in 6 hours. Find speed of A (in km/hr).

45

         420 km

A -------------------B 

Let the speed of A is S₁ km/h & that of B is S₂ km/h.

ATQ,

          \(\frac{420}{S_1 + S_2}\) = 7

       ⇒ S₁ + S₂ = 60 ------- (i)

A start moving 4 hours after B, Hence

4S₂ + (S₁ + S₂) × 6 = 420

Put the value of (S₁ + S₂) from eqn (i)

4S₂ + 60 × 6 = 420

4S₂ = 420 - 360

4S₂ = 60

  S₂ = 15 km/h

We have S₁ + S₂ = 60 km/h

             S₁ + 15 = 60

                       S₁ = 45 km/h