Question

radius of iron sphere is 0.21 cm .if density of iron is 7.80 g/cc ,calculate its mass

Answer 1

volume of iron sphere =4/3 πr^3
=4/3 × 22/7 ×(0.21)^3
=4/3 × 22/7 × 21×21×21/10^6 cm^3
=0.0388 cm^3

now,
mass =volume × density
=0.0388 × 7.8 g
=0.302 gram

Answer 2

Volume ofsphere=4/3×22/7×r^3
=4/3×22/7×0.21^3
=4/3×22/7×0.21×0.21×0.21
=88×441/1000000
=0.038

Density =mass/volume
7.80=mass/0.038
Mass=7.80×0.038
=0.2964 kg.