question_answer

Two men A and B walk from P to Q at a distance of 21 km at rates 3 and 4 km/h, respectively. Breaches Q and returns immediately and meets A at R. The distance from P to R is

A)  14 km        

B)  20 km

C)  16 km        

D)  18 km

Correct Answer: D

Solution :

Let the distance between P to R is x km. \[\triangleright \triangleright \] For B?s motion \[\triangleright \] For A?s motion Then, \[\frac{x}{3}=\frac{21}{4}+\frac{21-x}{4}\] \[\therefore \] \[7x=2\times 3\times 21\] \[\therefore \] \[x=18\]