Question

 A garden roller whose length is 3 m long and whose diameter is 2.8 m is rolled to level a garden. How much area will it cover in 8 revolutions?

422.4 sq.m

26.4 sq.m

211.2 sq.m

52.8 sq.m

Q. no 02: The radius of a conical tent is 7 m and the height is 24 m. Calculate its Curved Surface Area in square metres.

1364

550

264

528

Q. no 03: If the total surface area of a cone of radius 7 cm is 704 sq.cm, then find its slant height.

25 cm

26 cm

30 cm

24 cm

Q. no 04: If the base area of a hemispherical solid is 1386 sq. metres, then find its total surface area?

4178 sq.metres

4198 sq.metres

4158 sq.metres

4138 sq.metres

Q. no 05: Find the diameter of a sphere whose surface area is 154 sq.m.

(7/2) m

7 m

21 m

14 m

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Answer 1

Answer:

1.

circumference of circle = 2pir

= 2 x pi x 1.4

= 8.81 m

Area = length x breadth

= 8.81 x 3

= 26 .43 m^{2}

Area cover in 8 revolutions = 26.43 x 8

= 211.44 m^{2}

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2.

Area of the canvas = Curved surface area of the conical tent

Since the canvas is rectangular in shape, its area is = length × width

Curved surface area of a cone =πrl, where r is the radius of the cone and l is the slant height.

$For \: a \: cone \: , l= \sqrt{h { }^{2} } + \sqrt{r {}^{2} }$

where l is the slant height.

$Hence, l= \sqrt{24 {}^{2} } + \sqrt{7 {}^{2} }$

$⇒l= \: \: \sqrt{625}$

⇒l=25 cm

Hence, length ×5= 22/7 ×7×25

∴ length =110 m

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3.

Given :-

The total surface area of a cone of radius 7 cm is 704 cm².

To find :-

The slant height.

Solution :-

Let the slant height of the cone is l cm.

Radius = 7 cm

According to the question,

πr(r+l) = 704

→ (22/7) ×7 (7+l) = 704

→ 22(7+l) = 704

→ 7+l = 704/22

→ 7+l = 32

→ l = 32-7

→ l = 25

Therefore, the slant height of the cone is 25 cm.

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4.

Let r be the radius of the hemisphere.

Given that, base area = πr2 = 1386 sq. m

T.S.A. = 3πr2 sq.m

= 3 ×1386 = 4158

Therefore, T.S.A. of the hemispherical solid is 4158 m2

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5.

d≈7

A Surface area

154

Unit Conversion:

Using the formulas

A=4πr2

d=2r

Solving for d

d=A

π=154

π≈7.00141

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