Two slightly out of tune instruments will creat beats when the same note is played

This is the substance(s) formed in a chemical reaction.

Awater-filled u-tube manometer is used to measure the pressure inside a tank that contains air. the water level in the u-tube on the side that connects to the tank is 5 ft above the base of the tank. the water level in the other side of the u-tube (which is open to the atmosphere) is 2 ft above the base. determine the pressure within the tank.

Place me with this question is my last question