2013gmat wrote:
Somebody please explain this to me ?
Without getting into too much maths, lets solve this.
Lets call these asteroids X,Y,Z instead of X-13/14/15 etc for simplicity.
What is given in question:
1. Notice, Z was observed 2 extra seconds - or that mean Z travelled for 2 extra seconds than X and Y.
2. Distance Y traveled was 3 times X , in same duration. This would mean speed of Y is 3 times that of X. and difference is given as 2000.
Thus, Y traveled 3 times faster (say speed =3V) than X (say speed =V) and difference is 2000 => 3V-V =2000
Or V =1000.
3. Distance Z traveled was 5 times what X traveled despite having same speed.
Z traveled 5 times what X traveled despite having same speed because Z traveled 2 exta seconds. That means, extra 2 seconds = extra 4 times distance
=> original duration of travel for X (and for Y) = 0.5 seconds
So question has become, how much X traveled in 0.5 seconds with speed 1000 km/s.
So total distance covered by X = 1000* 0.5 = 500
Ans A it is.
Hope it is clear.