Q11 of 35 Page 311

The time which took today my friend Rajat running with uniform speed to round once of a circular field of school is 30 seconds less while he ran diametrically with same speed. Let us write by calculating the area of field of school if his speed is 9 meter/sec.

Given, speed of Rajat = 9 m /sec



Where distance is the perimeter of circular field


But perimeter = 2π r where r is the radius of circle


⇒ Time taken =


According to the given condition


Where r is radius of circular field and 2r = diameter


⇒


⇒ 2π r – 270 = 2r (taking LCM and cancelling 9 from both side)


⇒ 2π r – 2r = 270


⇒ r (π -1) = 135



⇒


Area of the circular field = πr2 where r is the radius


= m2


= 12474 m2


More from this chapter

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9

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 10

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 12

A equally wide path runs out-side the circular field of Bakultala. The length of outer circumference exceeds the inner circumference by 132 meter. If the area of path is 14190 sq. meter, let us write by calculating the radius of circular path.

 13

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