A person covers a distance in 9 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.  Choose the correct choice.
A) 18 m/s  B) 4 m/s  C) 15 m/s  D) 10 m/s  E) 6 m/s
6 m/sxplanation:   T = 9 m   Spees = 12 kmph   = 12 x 5/18 = 10/3 m/s   Let new speed be "x"   9 x (10/3) = 5x   x = 6 m/s   Answer: Option 6 m/s
<result>E</result>
A person covers a distance in 9 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.