1. The problem statement, all variables and given/known data In the attachment. 2. Relevant equations Chart of pressure loss due to friction for steel ducts : http://postimg.org/image/4iml9x761/ 3. The attempt at a solution I dont understand the deltaP/L column of the results table. Where did the values come from? Shouldn't they all be 0.063 in.wg / 100ft or 0.5 Pa/m since the principle of the equal friction method is to have the same pressure loss per length for the entire system?