- ✓$3$
- B$3.5$
- C$4$
- D$4.5$
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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$1.$ the selection of four red marbles.
$2.$ the selection of one white and three red marbles.
$3.$ the selection of one white, one blue and two red marbles.
$4.$ the selection of one marble of each colour.
The smallest total number of marbles satisfying the given condition is