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प्रश्न
Find the total surface area of an open pipe of length 50 cm, external diameter 20 cm and internal diameter 6 cm.
उत्तर
Length of an open pipe = 50 cm
External diameter = 20 cm `=>` External radius (R) = 10 cm
Internal diameter = 6 cm `=>` Internal radius (r) = 3 cm
Surface area of pipe open from both sides = 2πRh + 2πrh
= 2πh(R + r)
= `2 xx 22/7 xx 50 xx (10 + 3)`
= 4085.71 cm2
Area of upper and lower part = 2π(R2 – r2)
= `2 xx 22/7 xx (10^2 - 3^2)`
= `2 xx 22/7 xx (100 - 9)`
= `2 xx 22/7 xx 91`
= 572 cm2
Total surface area = 4085.714 + 572
= 4657.71 cm2
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