Question

已知两圆的半径和为27cm,面积和为369πcm²,则大圆半径是小圆半径的几倍?

Answer 1

+R=27 (1)

r^2+R^2=369 (2)

(1)^2==> r^2+R^2+2rR=729 (3)

(3)-(2) ==>2rR=360 ==>r=180/R

180/R+R=27

R^2-27R+180=0

R=[27±√(729-720)]/2

R1=15 R2=12

R=15 r=12 R/r=5/4