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Vidaara.orgClass 8 · Mathematics
CodeVID-M08-10-CLS-01
Classification of Triangles - Assignment
Chapter: Triangles
Topic: Classification of Triangles and Angle Properties
Maximum Marks: 35
Time: 75 minutes
Name: ____________________ Roll No.: __________ Date: ____________

General Instructions

  • All questions are compulsory.
  • Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
  • Show all working for Sections B, C and D. Only final answers are given at the end — for full solutions, raise your doubts with your teacher.
Section A — Multiple Choice Questions 5 × 1 = 5 marks
1.
The angle sum of a triangle is:
  • A.$90^\circ$
  • B.$180^\circ$
  • C.$270^\circ$
  • D.$360^\circ$
2.
Each angle of an equilateral triangle is:
  • A.$45^\circ$
  • B.$60^\circ$
  • C.$90^\circ$
  • D.$30^\circ$
3.
An exterior angle equals the sum of the two:
  • A.adjacent angles
  • B.opposite interior angles
  • C.right angles
  • D.exterior angles
4.
A triangle with a $90^\circ$ angle is:
  • A.acute
  • B.right-angled
  • C.obtuse
  • D.equilateral
5.
A scalene triangle has:
  • A.all sides equal
  • B.two sides equal
  • C.all sides different
  • D.a right angle
Section B — Short Answer (2 marks) 4 × 2 = 8 marks
6.
Two angles are $50^\circ$ and $60^\circ$. Find the third.
7.
Each angle of an equilateral triangle is:
8.
A right triangle has one angle of:
9.
How many equal sides does an isosceles triangle have?
Section C — Short Answer (3 marks) 4 × 3 = 12 marks
10.
Find the angles of a triangle in ratio $1:2:3$.
11.
The exterior angle is $120^\circ$ and one interior opposite angle is $50^\circ$. Find the other.
12.
Two angles of a triangle are equal and the third is $80^\circ$. Find each equal angle.
13.
Classify a triangle with sides $5, 5, 8$.
Section D — Long Answer (5 marks) 2 × 5 = 10 marks
14.
The angles of a triangle are $x,\ (x+20),\ (x+40)$. Find all three.
15.
An exterior angle is $110^\circ$ and the two interior opposite angles are equal. Find them and the third interior angle.

Answer Key

Section A — Multiple Choice Questions
  1. (B) $180^\circ$
  2. (B) $60^\circ$
  3. (B) opposite interior angles
  4. (B) right-angled
  5. (C) all sides different
Section B — Short Answer (2 marks)
  1. $70^\circ$.
  2. $60^\circ$.
  3. $90^\circ$.
  4. $2$.
Section C — Short Answer (3 marks)
  1. $30^\circ, 60^\circ, 90^\circ$.
  2. $70^\circ$.
  3. $50^\circ$.
  4. Isosceles.
Section D — Long Answer (5 marks)
  1. $40^\circ, 60^\circ, 80^\circ$.
  2. $55^\circ, 55^\circ$; third interior angle $70^\circ$.
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