Comprehension

Directions for questions: Read the information given below and answer the questions that follow :

A city has two perfectly circular concentric ring roads, the outer ring road (OR) being twice as long as the inner ring road (IR) . These are also four (straight line) chord roads form E1 , the east end point of OR to N2 , the north end point of IR; from N1 , the north end point of OR to W2 , the west end point of IR, from W1, the west end point of OR, to S2 , the south end point of IR; and from S1 , the south end point of OR to E2 , the east end point of IR. Traffic moves at a constant speed of 30
km/hr on the OR road, 20
km/hr on the IR road and 15√5 km/hr on all the chord roads.

CAT/2003

Question . 84

Amit wants to reach N2 from S1. It would take him 90 minutes if he goes on minor arc S1-E1 on OR, and then on the chord road E1-N2. What is the radius of the outer ring road in kms?