While covering a distance of 20 km Rakesh noticed that after walking for 1 hour and 30 minutes the d...........

Quantitative Aptitude (CDS) Time & distance

While covering a distance of 20 km, Rakesh noticed that after walking for 1 hour and 30 minutes, the distance covered by him was 3/5 of the remaining distance. What is his speed in meters per second?

20/7 m/sec

15/4 m/sec

25/18 m/sec

30/13 m/sec

Explanation:

Let the speed be x km/hour
Then, distance covered in 1 hour 30 minutes = 3x/2
Remaining distance = ( 20 - 3x/2) km.
3x/2 = 3/5 ( 20 - 3x/2)
3x/2 = 3/5 (40-3x)/2
5x = 40 - 3x
8x = 40
x = 5
hence speed = 5 km/hour = (5×5/18)m/sec
= 25/18 m/sec