In one second, a cylinder of water 2m (2000 mm) in height (length) and diameter 14mm (radius 7mm) has passed through the pipe. That cylinder of water has volumecubic millimeters. In one minute (60 seconds), 60 of those cylinders of water have passed through the pipe. That's cubic millimeters. There are 1000000 cubic millimeters in a liter, so that would be 18.4725648 liters of water passes through the pipe in 1 minute. Edwin