<prompt> The following information is available about the body fluid volumes of a normal male: total body water, 40 liters; intracellular water, 25 liters; plasma water, 4 liters. The volume of the interstitial water is?19 liters15 liters21 liters11 liters  <response>: Subtracting the intracellular water from the total body water gives the extracellular water 15 liters. Since the extracellular water exists primarily of the plasma water and the interstitial water, subtracting the plasma water 4 liters from the extracellular water 15 liters gives the interstitial water 11 liters. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. 2012. Chapter 1. General Principles Energy Production in Medical Physiology. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks Eds, Ganongs Review of Medical Physiology, 24e. 