If every side of a triangle is doubled, then increase in the area of the triangle is:
A$100\sqrt{2}\%$
B$200\%$
C$300\%$
D$400\%$
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C$300\%$
$\text{s}=\frac{\text{a}+\text{b}+\text{c}}{2},\text{A}=\sqrt{\text{s}(\text{s}-\text{a})(\text{s}-\text{b})(\text{s}-\text{c})}$
Now, if $a' = 2a, b' = 2b$ and $c' = 2c$
Then, $\text{s}'=\frac{\text{a}'+\text{b}'+c'}{2}=\frac{2\text{a}+2\text{b}+2\text{c}}{2}=2\text{s}$
$\text{A}'=\sqrt{\text{s}'(\text{s},-\text{a}')(\text{s}'-\text{b}')(\text{s}'-\text{c}')}$
$=\sqrt{2\text{s}(2\text{s}-2\text{a})(2\text{s}-2\text{b})(2\text{s}-2\text{c})}$
$=4\sqrt{\text{s}(\text{s}-\text{a})(\text{s}-\text{b})(\text{s}-\text{c})}$
$\Rightarrow\text{A}' = 4\text{A}$
⇒ Increase in Area $=\frac{4\text{A}-\text{A}}{\text{A}}\times100\%=300\%$
Hence, correct optin is $(c)$.
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