Q

Let triangle ABC similar triangle DEF and their areas be, respectively, 64 cm^ 2 and 121 cm ^ 2. If EF = 15.4 cm, find BC.

Q1  Let $\Delta ABC \sim \Delta DEF$ and their areas be, respectively, 64 $cm^2$ and 121 $cm^2$. If

EF = 15.4 cm, find BC.

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$\Delta ABC \sim \Delta DEF$              ( Given )

ar(ABC) = 64 $cm^2$ and ar(DEF)=121 $cm^2$.

EF = 15.4 cm                              (Given )

$\frac{ar(\triangle ABC)}{ar(\triangle DEF)}=\frac{AB^2}{DE^2}=\frac{BC^2}{EF^2}=\frac{AC^2}{DF^2}$

$\frac{64}{121}=\frac{BC^2}{(15.4)^2}$

$\Rightarrow \frac{8}{11}=\frac{BC}{15.4}$

$\Rightarrow \frac{8\times 15.4}{11}=BC$

$\Rightarrow BC=11.2 cm$

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