In a 100 meter race, A runs at a speed of 9 km/hr. He gives a start of 10 meter to B and still defeats him at 10 sec. Find speed of B?

\(\frac{9}{5}\) m/sec

A's time to cover 100 meter = \(\frac{100}{9 × \frac{5}{18}}\) = 40 sec.

Time taken by B to cover 90 meter = 40 + 10 = 50 sec.

B's speed = \(\frac{90}{50}\) = \(\frac{9}{5}\) m/sec.