Help with this physics problem please!?

Question

One cubic centimeter (1.0 cm3) of water has a mass of 1.0 10-3 kg.
(a) Determine the mass of 1.0 m3 of water.
1000 kg

(b) Assuming that biological substances are 98% water, estimate the masses of a cell with a diameter of 1.0 µm, a human kidney, and a fly. Take a kidney to be roughly a sphere with a radius of 4.0 cm and a fly to be roughly a cylinder 4.8 mm long and 2.0 mm in diameter.
a cell kg
a human kidney kg
a fly kg

Answer 1

a cell can be approximated to a sphere with a diameter = 1*10^-4 cm

r=0.5 * 10^-4 cm
V = 4/3 pi r^3
V = 4/3 pi (0.5 * 10^-4)^3 cm3
now take
V/ (.98)*(1gm / cm3) = mass of cell in gm
Do the same for Kidney
V= 4/3 pi r^3
r= 4 cm
mass = (4/3*pi*64) (1gm/cm3)/0.98

for the fly the cylinder formula is
V = L * 2 pi r^2
r = 0.2 / 2 cm = 0.1 cm
L = 0.48 cm
mass of fly = 2*pi*0.48*(0.1)^2 * 1gm/cm3 /0.98

all the answers are in gm, to convert to kg just divide by 1000.