The two cars A and B are moving with same speed as 25km/h in the direction shown in the above figure.
From the diagram, Relative velocity of carB with respect to car A,
vBA=vB−vA=√252+252=25√2km/h
i.e. vBA is 25√2km∕h at an angle of 45∘ from east towards north. ∴ Minimum distance between the two cars i.e distance of closest approach is equal AC=BAsin45∘. =50sin45∘=25√2km ∴ Time taken=