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Probability

Question

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A metal pipe is 77 cm long. The inner diameter of a cross section is 4 cm, the outer diameter being 4.4 cm. Find its

(i) inner curved surface area,
(ii) outer curved surface area,
(iii) total surface area.

Solution

h = 77 cm
2r = 4 cm

⇒ r = 2 cm
2R = 4.4 cm
⇒ R = 2.2 cm

(i) Inner curved surface area =

2 πrh

equals 2 cross times 22 over 7 cross times 2 cross times 77 equals 968 space cm squared

(ii) Outer curved surface area =

2 πRh

equals 2 cross times 22 over 7 cross times 2.2 cross times 77 equals 1064.8 space cm squared

(iii) Total surface area

equals 2 πRh plus 2 πrh plus 2 straight pi left parenthesis straight R squared minus straight r squared right parenthesis equals space 1064.8 plus 2 cross times 22 over 7 cross times 2 cross times 77 plus 2 cross times 22 over 7 cross times left curly bracket left parenthesis 2.2 right parenthesis squared minus left parenthesis 2 right parenthesis squared right curly bracket equals space 1064.8 plus 968 plus 2 cross times 22 over 7 cross times left parenthesis 4.84 minus 4 right parenthesis equals 1064.8 plus 968 plus 2 cross times 22 over 7 cross times 0.84 equals space 1064.8 plus 968 plus 5.28 equals 2038.08 space cm squared

Some More Questions From Probability Chapter

A cubical box has each edge 10 cm and another cuboidal box is 12.5 cm long, 10 cm wide and 8 cm high.

(i) Which box has the greater lateral surface area and by how much?

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(i) What is the area of the glass?
(ii) How much of tape is needed for all the 12 edges?

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A table cover 4 m x 2 m is spread on a table. Find the cost of polishing the top of the table at र40 per square metre of 25 cm table cover is hanging all round the table.

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Two cubes of side 6 cm each, are joined end to end. Find the surface area of the resulting cuboid.

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