Question

Find the radius of a circle whose circumference is equal to the sum of the circumferences of two circles of radii 15 cm and 18 cm.

NCERT Class X
Mathematics - Exemplar Problems

Chapter _AREA RELATED TO CIRCLES

Answer 1

Let radius of circle be r cm

2*22/7*r = (15*7/2*22) + (18*7/2/22)
or, 44*7*r = 7/2*22*(18+15)
or, r = 18+15 = 33

So, radiu of circle is 33cm

Answer 2

radius of circle is r cm  whose circumference is = to the sum of two circles circumference.

2x22/7xr = [15x7/2x22] + [18*7/2/22)]

and here ,

44x7xr = 7/2x22x[18+15]

r = 18+15 = 33

so that radius of a circle whose circumference is equal to sum of two circles circumference is 33 cm