Question

Let $△ABC\sim △DEF$ and their areas be, respectively, $64c{m}^2$ and $121c{m}^2$, If $EF=15.4cm$, find $BC$

Answer 1

$△ABC\sim △DEF$

$⟹\frac{Ar\left(\Delta ABC\right)}{Ar\left(\Delta DEF\right)}={\left(\frac{BC}{EF}\right)}^2\frac{64}{121}={\left(\frac{BC}{15.4}\right)}^{2}BC=\sqrt{\frac{64}{121}}\times 15.4BC=\frac{8}{11}\times 15.4=11.2cm$