Q11 of 68 Page 16

The sum of the radii of two circles is 140cm and the difference of their circumferences is 88cm. Find the diameters of the circles.


Let radius of first circle = r1cm


Let radius of second circle = r2cm


So,


r1 + r2 = 140cm …. (i)


2πr1 – 2πr2 = 88cm



r1 - r2 = 14cm …. (ii)


By adding equation 1 & 2



r1 = 77cm


From equation 1


77 + r1 = 140 cm


r2 = 140 – 77 = 63cm


r2 = 63cm


So,


Diameter of first circle = 2×r1 = 2×77 = 154cm


Diameter of second circle = 2×r2 = 2×63 = 126cm


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