MCQ
Consider a $\triangle A B C$ in the $X Y$-plane with vertices $A=(0,0), B=(1,1)$ and $C=(9,1)$. If the line $x=a$ divides the triangle into two parts of equal area, then a equals
  • $3$
  • B
    $3.5$
  • C
    $4$
  • D
    $4.5$

Answer

Correct option: A.
$3$
a
(a)

Given, in $\triangle A B C$

$A(0,0), B(1,1) C(9,1)$

$\text { Area of } \triangle C D E=\frac{1}{2} \text { Area of } \triangle A B C$ $\Rightarrow \quad \frac{1}{2} \times C D \times D E=\frac{1}{4} \times B C \times A P$ $\Rightarrow \quad \frac{1}{2}(9-a) \times\left(1-\frac{a}{9}\right)=\frac{1}{4} \times 8 \times 1$

$\Rightarrow \quad (9-a)(9-a)=36$

$\Rightarrow \quad 9-a=6 \Rightarrow a=3$

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