Question

27 solid iron spheres each of radius x cm are melted to form a sphere with radius y cm,find the ratio of x:.

Answer 1

Radius of 1 solid iron sphere =r

⇒Volume =34πr3

⇒Volume of 27 solid iron spheres =27×34πr3

⇒34πr′3=27×34πr3

r′3=2πr3

⇒r′=3r

(ii) Surface area =4πr2

SA r′=4πr′2

=4π(3r)2=36πr2

S′S=36πr24πr2=91=1:9