Given that,
m= 45 kg = 45000g
A = 900 cm2
Ρ = 1000 kg/m3 = 1 g/cm3
Let, the difference in the height of the water level be h units.
Now,
According to the figure
Pa+hρg=Pa+mgA
h=mAρ
Put the values of all elements
h=45×1000900×1
h=50cm
Hence, the difference in the levels of water in the two tubes is 50 cm.