S.chand class 6 Mathematics Chapter 20 Exercise 20A

 Exercise 20A

Question 1

1. In the adjoining figure, name

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(i) the side opposite to $\angle R$

(ii) the angle opposite to QR.

(iii) the vertex opposite to $P R$.

(iv) the side opposite to vertex $P$.



2. (i) Name the points which are in the triangular region $A B C$. Which of these lie on the $\triangle A B C$ ?

(ii) Which points lie in the exterior of $\triangle A B C$ ?

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3. State for each triangle whether it is scalene, isosceles or equilateral.

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4.State for each of the triangle shown in the figures whether it is acute, right or obfuse.

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5. Classify the triangles the measures of whose sides are given below as scalene, isosceles or equilateral.

(i) $3 \mathrm{~cm}, 4 \mathrm{~cm}, 5 \mathrm{~cm}$

(iv) $5.5 \mathrm{~cm}, 5.5 \mathrm{~cm}, 5.5 \mathrm{~cm}$

(ii) $6.8 \mathrm{~cm}, 8 \mathrm{~cm}, 6.8 \mathrm{~cm}$

(iii) $7.8 \mathrm{~cm}, 8.7 \mathrm{~cm}, 9.3 \mathrm{~cm}$

(v) $x \mathrm{~cm}, y \mathrm{~cm}, x \mathrm{~cm}$

(vi) $x \mathrm{~cm}, \times \mathrm{cm}, \times \mathrm{cm}$


6. Classify the triangles whose angles measures are given below, as acute, obtuse or right.

(i) $39^{\circ}, 58^{\circ}, 83^{\circ}$

(iv) $31^{\circ}, 109^{\circ}, 40^{\circ}$

(ii) $20^{\circ}, 65^{\circ}, 95^{\circ}$

(iii) $30^{\circ}, 60^{\circ}, 90^{\circ}$

(v) $44^{\circ}, 46^{\circ}, 90^{\circ}$

(vi) $48^{\circ}, 56^{\circ}, 76^{\circ}$


7. Look at the figure given alongside 

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(i) Name the equilateral triangles.

(ii) Name the isosceles triangles.

(iii) Name the scalene triangles.

(iv) Name the acute triangles.

(v) Name the obtuse triangles, i.e., obtuse-angled triangles.

(vi) Name the right triangles.


8. All equilateral triangles are isosceles, but not all isosceles triangles are equilateral. Why?


9. How many different triangles are there in the given figure. Name each of them.

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Multiple Choice Question (MCQ) 
Tick (✔) the correct option.

10. Based on the angle measures given, which of the following represents an isosceles obtuse triangle?

(a) $45^{\circ}, 45^{\circ}, 90^{\circ}$

(b) $46^{\circ}, 46^{\circ}, 88^{\circ}$

(c) $42^{\circ}, 42^{\circ}, 96^{\circ}$

(d) $60^{\circ}, 60^{\circ}, 60^{\circ}$



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