A and B go around a circular track of length 1800 m on a cycle at speeds of 36 kmph and 54 kmph. After how much time will they meet for the first time at the starting point? Choose the correct choice from the following options
A) 120 sec  B) 165 sec  C) 186 sec  D) 167 sec  E) 360 sec

Rationale: time taken to meet for the first time at the starting point = lcm { length of the track / speed of a , length of the track / speed of b } = lcm { 1800 / ( 36 * 5 / 18 ) , 1800 / ( 54 * 5 / 18 ) } = lcm ( 180 , 120 ) = 360 sec . answer : e
Answer: E