delhi is at a distance of 250 km from chandigarh.A sets out from chandigarh at a speed of 80 km/hr and B sets out at the same time from delhi at a speed of 45 km/hr . when will they meet each other?

Here, V_a = 80 km/hr
V_b = 45 km/hr
Relative velocity of one w.r.t another :
_Vab = V_a - V_b
     = 80- (-45) = 125 km/hr
Time taken to cover a distance of 250 km with a speed of 125 km/h = $\frac{250}{125} = 2 hours$
Hence, they will meet after 2 hours from the start.