Answer:
1.5 cm
Step-by-step explanation:
The ratio of areas is the square of the ratio of diameters, so cylinder A has (1/2)^2 = 1/4 the area of cylinder B.
The volume of the cylinder is jointly proportional to its area and its height. So, for a fixed volume, the height is inversely proportional to the area.
Cylinder B has 4 times the area of cylinder A, so any volume moved from cylinder A to B will require only 1/4 of the change in height that is required in cylinder A.
The red piston in cylinder B rises 1.5 cm.