Calculate the velocity of water coming out of a double-entry pipe

If we know the volumetric flow rates of the water going into the two branches, then what would be the velocity of the water coming out?

Brain Teaser: A Sliding Ladder

A 25 ft ladder (assume it is not an extension ladder) is placed with its foot 7 ft away from a building. If the top of the ladder slips down 4 ft, how many feet will the bottom slide out?