Walking at 4/7 of its usual speed, a train is 9 minutes late. Find its usual time to cover the journey. Select: A) 8 min . B) 10 min . C) 12 min . D) 15 min . E) 17 min .

Rationale: explanation : solution : new speed = 4 / 7 of the usual speed . let usual time be x . . ' . new time taken = 7 / 4 of usual time = 7 x / 4 so , ( 7 x / 4 ) - x = 9 min . = > 3 x = 36 = > x = 12 min . answer : c
Answer: C