In a hydraulic system, piston 1 has a surface area of 100 cm2, and piston 2 has a surface area of 900 cm2. Piston 1 exerts a pressure of 10 Pa on the fluid in the hydraulic lift.

What is the fluid pressure on piston 2?

By hydraulic principles the pressures are equal.

Then pressure on piston 2 = pressure on piston = 10 Pa.

That is what permits to apply a low force on the surface of the piston with the smaller area and get a bigger force on sureface of the piston with the greater area.