Question

11. The external and internal diameters of a circular path are 12 m and 8 m respectively. The area of the circular path is (a) 9 m? (b) 16 mº (c) 20 m (d) 36 m²



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Answer 1

Answer:

Step-by-step explanation:

given,

the external diameter, D = 12m

and internal diameter, d = 8m

=> area of the circular path = diff. between the areas of external & internal circles

                                              = (22/7)(R²-r²)

where R and r are the external and internal radius resply.,

so, R = D/2 = 12/2 = 6m

and r = d/2 = 8/2 = 4m

so, the area of the circular path =  (22/7) * (6²-4²) m²

                                                     =  (22/7) * (36-16) m²

                                                     =  (22/7) * 20 m²

ie., 20π m²

which is option (c),

(i guess so. please check your book whether you missed that pi part.)

Answer 2

Given: The external and internal diameters of a circular path are 12 m and 8 m respectively.

To find: The area of the circular path.

Solution:

• The area of a circle is given by the formula,

       $A = \pi r^{2}$

• Here, A is the area of the circle and r is the radius of the circle.
• Radius is the half of the diameter, so the external and internal radii of the circular path are 6 m and 4 m, respectively.
• Area of the entire circular surface is given by,

       $A = \frac{22}{7} * 6m * 6m$

           $= 113.14m^{2}$

• Area of the inner circular surface is given by,

       $A = \frac{22}{7} * 4m * 4m$

           $= 50.29m^{2}$

• So, the value of the area of the circular path is given by,

       $A_{path} = 113.14 - 50.29$

                 $= 62.85m^{2}$

Therefore, the area of the circular path is 62.85 m².