P₂-P₁=225π
r₂-r₁=5
P=πr²
πr₂²-πr₁²=225π
π(r₂²-r₁²)=225π
r₂²-r₁²=225
r₂=5+r₁
(5+r₁)²-r₁²=225
25+10r₁+r₁²-r₁²=225
10r₁=200
r₁=20
r₂=5+20=25
Obw=2πr
r=20cm
Obw=40πcm
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P₂-P₁=225π
r₂-r₁=5
P=πr²
πr₂²-πr₁²=225π
π(r₂²-r₁²)=225π
r₂²-r₁²=225
r₂=5+r₁
(5+r₁)²-r₁²=225
25+10r₁+r₁²-r₁²=225
10r₁=200
r₁=20
r₂=5+20=25
Obw=2πr
r=20cm
Obw=40πcm