Let the speed of the fastest runner = x and the speed of the slower runner = y Relative speed (same direction) = x - y Relative speed (opposite direction) = x + y According to the question,
720
x+y
= 36 (x + y) 36 = 720 36x + 36y = 720 ⇒ x + y = 20 ……(i)
720
x−y
= 180 (3 minutes) x − y ⇒ x - y = 4 ……(ii) Equating (i) and (ii), we get x = 8 m/sec and y = 12 m/sec So, speed of the fastest runner is 12 m/sec