Question

find the total surface area of a hollow cylinder open at both ends if its lengtg is 28cm external radius is 7cm & thickness is 1cm (ans--2369.71cm²)​

Answer 1

Step-by-step explanation:

external radius (R) = 7cm

so total external surface area = 2πRh

= 2 ×3.14×7×28 = 1230.88 cm²

now

internal radius (r) = R - thickness

= 7-1 = 6cm

now internal surface area = 2πrh

= 2×3.14×6×28 = 1055.04cm²

now total area = 1230.88+1055.04

= 2285.92cm²