MCQ
$\Rightarrow\triangle\text{ABC}\sim\triangle\text{DEF}$ such that $\text{ar}(\triangle\text{ABC})=36\text{ cm}^2$ and $\text{ar}(\triangle\text{DEF})=49\text{ cm}^2.$ Then, the ratio of their corresponding sides is :
  • A
    $36 : 49$
  • $6 : 7$
  • C
    $7 : 6$
  • D
    $\sqrt{6}:\sqrt{7}$

Answer

Correct option: B.
$6 : 7$
$\Rightarrow\triangle\text{ABC}\sim\triangle\text{DEF}$
$\Rightarrow\frac{\text{ar}(\triangle\text{ABC})}{\text{ar}(\triangle\text{DEF})}=\frac{\text{AB}^2}{\text{DE}^2}$
$\Rightarrow\frac{36}{49}=\frac{\text{AB}^2}{\text{DE}^2}$
$\Rightarrow\frac{\text{AB}}{\text{DE}}=\frac{6}{7}$
Since the triangle are similar,
$\frac{\text{AB}}{\text{DE}}=\frac{\text{BC}}{\text{EF}}=\frac{\text{AC}}{\text{DF}}=\frac{6}{7}$
So, the ratio is $6 : 7.$

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