A rectangular strip 25 cm × 7 cm is rotated about the longer side. Fi

1.	A rectangular strip 25 cm × 7 cm is rotated about the longer side. Find the total surface area of the solid thus generated.
Answer» We have, Dimension of rectangular strip = 25 cm × 7 cm When this strip is rotated about its longer side, Height of cylinder becomes = 25 cm Radius = 7 cm ∴ Total surface area of cylinder = 2πr (h+r) = 2 × 22/7 × 7 (25 + 7) = 2 × 22/7 × 7 × 32 = 1408 cm²

A rectangular strip 25 cm × 7 cm is rotated about the longer side. Find the total surface area of the solid thus generated.

Answer»

We have,

Dimension of rectangular strip = 25 cm × 7 cm

When this strip is rotated about its longer side,

Height of cylinder becomes = 25 cm

Radius = 7 cm

∴ Total surface area of cylinder = 2πr (h+r)

= 2 × 22/7 × 7 (25 + 7)

= 2 × 22/7 × 7 × 32

= 1408 cm²