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प्रश्न
A rectangular strip 25 cm × 7 cm is rotated about the long side. Find The total surface area of the solid thus generated.
उत्तर
We have,
Dimension of rectangular strip = 25 cm × 7 cm
When this strip is rotated about its longer side,
The height of the cylinder becomes = 25 cm
Radius = 7 cm
∴ The total surface area of the cylinder = 2πr(h + r)
= `2 xx 22/7 xx 7(25 + 7)`
= `2 xx 22/7 xx 7 xx 32`
= 1408 cm2
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