Question Number 61069 by aanur last updated on 28/May/19
Commented by aanur last updated on 28/May/19
$${Find}\:{S}\mathrm{20}^{} \\ $$$${Could}\:{you}\:{help}\:{me}\:{sir} \\ $$
Commented by kaivan.ahmadi last updated on 29/May/19
$$\mathrm{4}{a}+\mathrm{38}{d}=\mathrm{72}\Rightarrow\mathrm{2}{a}+\mathrm{19}{d}=\mathrm{36} \\ $$$${S}_{\mathrm{20}} =\mathrm{10}\left(\mathrm{2}{a}+\mathrm{19}{d}\right)=\mathrm{10}×\mathrm{36}=\mathrm{360} \\ $$