Question

Let $\Delta ABC\sim \Delta DEF$. If $ar\left(\Delta ABC\right)=100{cm}^2,ar\left(\Delta DEF\right)=196{cm}^2$ and $DE=7cm$, then find $AB$.

Answer 1

${AB}^2/{DE}^2=area\left(△ABC\right)/area\left(△DEF\right){AB}^2/7^2=100/196{AB}^2=100\ast 49/196{AB}^2=25AB=5$

AB = 5 cm