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The internal and external diameters of a metallic pipe are 44 cm and 46 cm resptly. The pipe is painted from outside and inside. The total cost of painting at the rate of rs.2.50 per square metre is rs.99. Caculate the length of the pipe |
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Answer» N, Inner radius(r)=2cm Outer diameter(D)=4.4cm Length of metal pipe=77cm If outer sphere diameter =4.4cm, then, it's radius= 2 4.4
∴ Outer sphere radius(R)=2.2cm Now, let US find inner CURVED surface area=? As we know that, Surface area of a sphere =2πrh sq.cm where, π= 7 22
,r=2cm,h=77cm ∴ Inner curved surface area=2× 7 22
×2×77 =44×22 sq. cm =968 sq. cm ∴ Inner curved surface area(s 1
)=968 sq.cm Now, let us find outer curved surface area, as, we know that, Surface area of outer sphere=2πRh sq. cm where, π= 7 22
, R=2.2cm, h=77cm so, we get, Outer curved surface area=2× 7 22
×2.2×77cm 2
=22×2×2.2×11cm 2
=44×2.2×11cm 2
=1064.8 sq.cm ∴ Outer curved surface area(s 2
)=1064.8 sq. cm Now let us find total surface area as, we know that, Total surface area = Inner surface area (s 1
)+Outer surface area (s 2
) T.S.A=[968+1064.8]sq. cm ⇒ T.S.A=2,032.8 sq.cm ∴ Total surface area(s)=2032.8cm 2 . |
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