Time taken by cyclist to cover the distance AB=60min Given, starting from 10: 01 am, every minute a motor cycle leaves A and moves towards B. Forty-five such motor cycles reach B by 11am. Also, the speed of all the motor cycles is same. That means that the 45 th moto cycle which started at 10: 45 am, reached B exactly at 11 am. Rest all reached B some time before B. Therefore, each motor cycle takes 15 min to cover the distance AB. Now, if the cyclist doubles his speed, then he will reach B in 30 min i.e. at 10: 30 am. So, the 15 th motor cycle (started at 10: 15 am from A) would be the last motor cycle to reach point B at 10: 30 am. Hence, there will be 15 motor cycles would have reached B by the time the cyclist reached B.