Answer :
volume of cylinder=πh(R²-r²)
=5120π
5120π=20πr²
5120=20r²
√256=r
⇒r=16
=5120π
5120π=20πr²
5120=20r²
√256=r
⇒r=16
Volume of hollow cylinder = πh(r1²-r2²)
= π * 40 * (12²-4²)
= π * 40 *128
=5120π cm³
Volume of solid cylinder = π r² h = volume of hollow cylinder
π r² 20 = 5120 π
r² = 5120/20
r² = 256
r = √256
r = 16 cm
= π * 40 * (12²-4²)
= π * 40 *128
=5120π cm³
Volume of solid cylinder = π r² h = volume of hollow cylinder
π r² 20 = 5120 π
r² = 5120/20
r² = 256
r = √256
r = 16 cm