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The circumference of a circle whose area...

The circumference of a circle whose area is `81 pi r^2`, is

A

`9 pir`

B

`18 pir`

C

`3 pir`

D

`81 pir`

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NCERT EXEMPLAR-PERIMETER AND AREA-Exercise
  1. What is the radius of the largest circle that can be cut out of the re...

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  2. The perimeter of the figure ABCDEFGHIJ is

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  3. The circumference of a circle whose area is 81 pi r^2, is

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  4. The area of a square is 100 cm. The circumference (in cm) of the large...

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  5. If the radius of a circle is tripled, the area becomes

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  6. The area of a semicircle of radius 4t is

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  7. All triangles have the same base and the same altitude. True or false.

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  8. All triangles are congruent. True or false.

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  9. All triangles are equal in area. True or false.

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  10. All triangles have the same perimeter. True or false.

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  11. In Fig. 9.29 ratio of the area of triangle ABC to the area of triangle...

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  12. Triangles having the same base have equal area. True or false

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  13. Ratio of circumference of a circle to its radius is always 2 pi : I.

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  14. 5 hectare = 500 m^2

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  15. An increase in perimeter of a figure always increases the area of the ...

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  16. Two figures having the same area cannot have different perimeters. Tru...

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  17. If area of a parallelogram is 24 cm^2 and one of the side is of length...

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  18. A hedge boundary needs to be planted around a rectangular lawn of size...

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  19. The perimeter of a rectangle is 40 m. Its length is four metres less t...

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  20. A wall of a room is of dimensions 5 mx 4 m. It has a window of dimensi...

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