Physics pressure question?

(a)
Volume of water column
= Mass / Density
= (0.200 kg) / (1.00 × 10³ kg/m³)
= 2 × 10⁻⁴ m³
= (2 × 10⁻⁴ m³) × (100 cm/m)³
= 200 cm³

Length of the water column
= (Volume of the water column) / A₂
= (200 cm³) / (10 cm²)
= 20 cm


(b)
After addition of water :

Sum of the volumes of the liquids above the original liquid level = 200 cm³
A₁ × h + A₂ × H = 200 cm³
(20.0 cm²) × (2.15 cm) + (10.0 cm²) × H = 200 cm³
H = 15.7 cm

Liquid pressure at the original liquid level :
(Density of the liquid) × g × h = (Density of the water) × g × H
(Density of the liquid) × 2.15 = (1.00 × 10³ kg/m³) × 15.7
Density of the liquid = (1.00 × 10³ kg/m³) × (15.7/2.15) = 7.30 × 10³ kg/m³

For a start, obviously the unknown liquid is more dense than water, or the water level would not be above the unknown liquid level.
a) 200g of water has a volume of 200cc., and as the area is 10cm^2 of the right side, the water column length is (200/10) = 20cm.
Volume of unknown liquid rise = (2.15 x 20cm^2) = 43cc.
b) (200/43) x 1g/cc. = unknown liquid density of 4.65g/cc., or 4,650 kg/m^3.