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Assertion (A) & Reason (B) MCQ

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MCQ 11 Mark
Statement-1 ( $\Lambda$ ): If the shadow of a verlical pole is $\frac{1}{\sqrt{3}}$ of its height, then the altitude of the sum is $60^{\circ}$
Slatement-2 (R): If the sun's altitude is $45^{\circ}$, then the shadow of a vertical pole is same as its
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  • A
    Statement-1 and Statement-2 are True; Statement-2 is a correct explanation for Statement-1.
  • Statement-1 and Statement-2 are True; Statement-2 is not a correct explanation for Statement-1.
  • C
    Statement- 1 is True, Statement- 2 is False.
  • D
    Statement-1 is False, Statement- 2 is True.
Answer
Correct option: B.
Statement-1 and Statement-2 are True; Statement-2 is not a correct explanation for Statement-1.
(B)Statement-1 and Statement-2 are True; Statement-2 is not a correct explanation for Statement-1.
Let $P Q$ be a vertical pole of height $h$ such that its shadow is of length $\frac{h}{\sqrt{3}}$. Let the sun's altitude be 0 . Then,
$
\tan \theta=\frac{h}{h / \sqrt{3}}=\sqrt{3} \Rightarrow \tan \theta=\tan 60^{\circ} \Rightarrow \theta=60^{\circ}
$
Thus, statement-1 is true.
Let $A B$ be a vertical pole of height/ $/$ metre and $A C$ be the length of its shadow when sun's altitude is $45^{\circ}$ (see Fig.).
In $\triangle B A C$, we obtain
$
\tan 45^{\circ}=\frac{\Lambda B}{\Lambda C} \Rightarrow 1=\frac{h}{\Lambda C} \Rightarrow A C=h
$
Hence, the shadow $A C$ of pole $A B$ is of the same height as that of the pole. So, statement- 2 is true,
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MCQ 21 Mark
Statement-1 (A): If the angles of elevation of the top of a tower from the points at distances of 9 m and 16 m from the base of $a$ tower in the same line are complementary, then the height of the tower is 12 m .
Statement-2 (R): If the angle of elevation of a tower from two points at distances of $a$ and $b$ from its foot and in the same straight line with it are complementary, then the height of the tower is $\sqrt{a b}$.
  • Statement-1 and Statement-2 are True; Statement-2 is a correct explanation for Statement-1.
  • B
    Statement-1 and Statement-2 are True; Statement-2 is not a correct explanation for Statement-1.
  • C
    Statement- 1 is True, Statement- 2 is False.
  • D
    Statement-1 is False, Statement- 2 is True.
Answer
Correct option: A.
Statement-1 and Statement-2 are True; Statement-2 is a correct explanation for Statement-1.
(A)Statement-1 and Statement-2 are True; Statement-2 is a correct explanation for Statement-1.
Let PQ be a tower of height $h$ metres such that the angles of elevation of its top observed from points $A$ and $B$ at distances $a$ and $b$ from the base of the tower are complementary. In right triangles $A P Q$ and $B P Q$, we obtain
$\begin{array}{ll} & \tan \theta=\frac{h}{a} \text { and } \tan \left(90^{\circ}-\theta\right)=\frac{h}{b} \\ \Rightarrow & \tan \theta=\frac{h}{a} \text { and } \cot \theta=\frac{h}{b} \\ \Rightarrow \quad & \tan \theta \times \cot \theta=\frac{h}{a} \times \frac{h}{b} \Rightarrow 1=\frac{h^2}{a b} \Rightarrow h=\sqrt{a b}\end{array}$
Thus, statement-2 is true
Using statement-2, we find that the height $h$ of the tower in statement-1 is given by $h=\sqrt{9 \times 16}$ $m =12 m$. So, statement -1 is also true and statement -2 is a correct explanation for statement -1 . Hence, option (a) is correct.
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Assertion (A) & Reason (B) MCQ - Maths STD 10 Questions - Vidyadip