Let the inner radius (ri)=rcm And the outer radius (r0)=(r+10)cm According to the question, π(r+10)2−πr2=3080 [∵ Area of circle =πr2] ⇒π(r2+100+20r−r2)=3080 ⇒(20r+100)=
3080
22
×7 ⇒(20r+100)=980 ⇒20r=980−100=880 ∴ri=44m and r0=r+10 =44+10=54m So, sum of two radii =54+44=98m