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True False[1 Marks ]

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6 questions · timed · auto-graded

Question 11 Mark
Write True or False in the following. Give reasons for your answer:
A triangle ABC can be constructed in which $\angle\text{B}=105^\circ, \angle\text{C}=90^\circ$ and AB + BC + AC = 10cm.
Answer
False.Solution:
Here, $\angle\text{B}=105^\circ, \angle\text{C}=90^\circ$ and AB + BC + CA = 10cm We know that, sum of angles of a triangle is 180° $\angle\text{A}+\angle\text{B}+\angle\text{C}=180^\circ$ Here, $\angle\text{B}+\angle\text{C}=105^\circ+90^\circ$ $=195^\circ>180^\circ$ which is not true. Thus, $\triangle\text{ABC}$ with given conditions cannot be constructed.
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Question 21 Mark
Write True or False in the following. Give reasons for your answer:
An angle of 52.5° can be constructed.
Answer
True.Solution:
To construct an angle of 52.5° firstly construct an angle of 90°, then construct an angle of 120° and then plot an angle bisector of 120° and 90° to get an angle 105°(90° + 15°). Now, bisect this angle to get an angle of 52.5°
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Question 31 Mark
Write True or False in the following. Give reasons for your answer:
A triangle ABC can be constructed in which $\angle\text{B}=60^\circ, \angle\text{C}=45^\circ$ and AB + BC + AC = 12cm.
Answer
True.
Solution:
We know that, sum of angles of a triangle is 180°
$\angle\text{A}+\angle\text{B}+\angle\text{C}=180^\circ$
Here, $\angle\text{B}+\angle\text{C}=60^\circ+45^\circ=105^\circ<180^\circ$
Thus, $\triangle\text{ABC}$ with given conditions can be constructed.
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Question 41 Mark
Write True or False in the following. Give reasons for your answer:
A triangle ABC can be constructed in which AB = 5cm, $\angle\text{A}=45^\circ$ and BC + AC = 5cm.
Answer
False.
Solution:
Here AB = BC + AC = 5cm. Since sum of two sides of a triangle is always greater than the third side, so we cannot construct a triangle in which AB = BC + AC.
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Question 51 Mark
Write True or False in the following. Give reasons for your answer:
A triangle ABC can be constructed in which BC = 6cm, $\angle\text{C}=30^\circ$ and AC - AB = 4cm.
Answer
True.Solution:
Since difference of two sides of a triangle is always smaller than the third side. Here, AC - AB (= 4 cm) < BC (= 6cm). Therefore, the given triangle can be constructed and given statement is true.
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Question 61 Mark
Write True or False in the following. Give reasons for your answer:
An angle of 42.5° can be constructed.
Answer
False.Solution:
Since, $42.5^\circ=\frac{1}{4}\times85^\circ$ and 85° cannot be constructed by using ruler and compass. Also 42.5° is not the multiple of 3. Therefore, an angle of 42.5º can not be constructed.
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True False[1 Marks ] - MATHS STD 9 Questions - Vidyadip