Question Number 69609 by TawaTawa last updated on 25/Sep/19
Commented by Prithwish sen last updated on 25/Sep/19
$$\mathrm{I}\:\mathrm{think} \\ $$$$\mathrm{The}\:\mathrm{area}\:\mathrm{of}\:\mathrm{inner}\:\mathrm{section}\:=\:\pi\left(\mathrm{75}\right)^{\mathrm{2}} \mathrm{sq}.\:\mathrm{cm} \\ $$$$\mathrm{The}\:\mathrm{area}\:\mathrm{of}\:\mathrm{outer}\:\mathrm{section}\:=\:\pi\left(\mathrm{100}−\mathrm{75}\right)\left(\mathrm{100}+\mathrm{75}\right) \\ $$$$=\:\pi×\mathrm{25}×\mathrm{175}\:\mathrm{sq}.\:\mathrm{cm}\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\: \\ $$$$\therefore\:\boldsymbol{\mathrm{Total}}\:\boldsymbol{\mathrm{cost}}\:=\:\boldsymbol{\pi}×\mathrm{75}×\mathrm{75}×\mathrm{2500}+\boldsymbol{\pi}×\mathrm{25}×\mathrm{175}×\mathrm{1500} \\ $$$$\boldsymbol{\mathrm{now}}\:\boldsymbol{\mathrm{do}}\:\boldsymbol{\mathrm{the}}\:\boldsymbol{\mathrm{calculation}} \\ $$
Commented by TawaTawa last updated on 25/Sep/19
$$\mathrm{God}\:\mathrm{bless}\:\mathrm{you}\:\mathrm{sir} \\ $$