Area Problems
A person observed that he required 30 s time to cross a circular ground along its diameter than to cover it once along the boundary. If his speed was 30m/min, than the radius of the circular ground is (take ? = 22/7)
Let the radius of circular field = r m.Speed of person in m/s = 30/60 = 1/2m/sAccording to the question,[(2?r) /(1/2)] - [(2r)/(1/2)] = 30? 4?r - 4r = 30? [4 x (22/7) - 4]r =30? (125 - 4)r = 30 ? (8.5)r = 30? r = 30/8.5 = 3.5 m
Let the diagonal of one square be (2d) cmThen, diagonal of another square = d cm? Area of first square = [ 1/2 x (2d)2] cm2Area of second square = (1/2 x d2) cm2? Ratio of area = (2d)2/ d2= 4/1 = 4: 1
Diameter of the circle = 13 + 5 = 18 cm? Radius = Diameter/2 =18/2 = 9 cm Area of the circle = ?r2 = (22/7) x 92 = (22 x 81)/9 = 1782/7 = 254.57 sq cm= 255 sq cm
EXAMIANS