A person covers a distance in 15 minutes. If runs at a speed of 12 km per hour on an average. Find the speed at which he must run to reduce the time of journey to 5 minutes.  Select:
A) 18 m/s  B) 4 m/s  C) 15 m/s  D) 10 m/s  E) 5 m/s
Explanation:   T = 15 m   Spees = 12 kmph   = 12 x 5/18 = 10/3 m/s   Let new speed be "x"   15 x (10/3) = 5x   x = 10 m/s   Answer: Option 10 m/s
<result>D</result>
A person covers a distance in 15 minutes. If runs at a speed of 12 km per hour on an average. Find the speed at which he must run to reduce the time of journey to 5 minutes.