Ramesh and Sohan start walking away from each other from a point P at an angle of 120°. Ramesh walks at a speed of 3 km/hour while Sohan walks at a speed of 4 km/hour. What is the distance between them after 90 minutes?

The distance covered by Ramesh in 90 minutes = 1.5*3 = 4.5 kms

Similarly the distance covered by Sohan in 90 minutes = 1.5*4 = 6 kms

The distance between Sohan and Ramesh after 90 minutes will be :

                               Cos(A) = $$\frac{b^{2}+c^{2}-a^{2}}{2bc}$$

                                     Cos(120) = $$\frac{4.5^{2}+6^{2}-d^{2}}{2*4.5*6}$$

                                                $$d^{2}$$ = $$4.5^{2}+6^{2}-2*4.5*6*Cos(120)$$

                                                        $$d^{2}$$ = 20.25+36+27 = 83.25

                                                              d =  $$\sqrt{83.25}$$

                                                             $$d \approx 9.12$$