Number of hours Pipe A requires to fill an empty tank : 10 hours
Number of hours Pipe B requires to fill an empty tank : 15 hours
Amount of water filled by Pipe A in empty tank in one hour: \(\frac{1}{10}\)
Amount of water filled by Pipe B in one hour: \(\frac{1}{15}\)
Amount of water filled by Pipe A and Pipe B together in one hour: \(\frac{1}{10}+\frac{1}{15}=\frac{5}{30}=\frac{1}{6}\)
∴ They can fill the tank together in 6 hours.