#### Chapters

Chapter 2: Rational Numbers

Chapter 3: Fractions (Including Problems)

Chapter 4: Decimal Fractions (Decimals)

Chapter 5: Exponents (Including Laws of Exponents)

Chapter 6: Ratio and Proportion (Including Sharing in a Ratio)

Chapter 7: Unitary Method (Including Time and Work)

Chapter 8: Percent and Percentage

Chapter 9: Profit, Loss and Discount

Chapter 10: Simple Interest

Chapter 11: Fundamental Concepts (Including Fundamental Operations)

Chapter 12: Simple Linear Equations (Including Word Problems)

Chapter 13: Set Concepts (Some Simple Divisions by Vedic Method)

Chapter 14: Lines and Angles (Including Construction of angles)

Chapter 15: Triangles

Chapter 16: Pythagoras Theorem

Chapter 17: Symmetry (Including Reflection and Rotation)

Chapter 18: Recognition of Solids (Representing 3-D in 2-D)

Chapter 19: Congruency: Congruent Triangles

Chapter 20: Mensuration

Chapter 21: Data Handling

Chapter 22: Probability

## Chapter 15: Triangles

### Selina solutions for Concise Mathematics Class 7 ICSE Chapter 15 Triangles Exercise 15 (A)

**State, if the triangle is possible with the following angles :**

20°, 70°, and 90°

**State, if the triangle is possible with the following angles :**

40°, 130°, and 20°

**State, if the triangle is possible with the following angles :**

60°, 60°, and 50°

**State, if the triangle is possible with the following angles :**

125°, 40°, and 15°

If the angles of a triangle are equal, find its angles.

In a triangle ABC, ∠A = 45° and ∠B = 75°, find ∠C.

In a triangle PQR, ∠P = 60° and ∠Q = ∠R, find ∠R.

**Calculate the unknown marked angles of the following figure :**

**Calculate the unknown marked angles of the following figure :**

**Calculate the unknown marked angles of the following figure :**

**Find the value of the angle in the given figure:**

**Find the value of the angle in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**In the given figure, show that: ∠a = ∠b + ∠c**

(i) If ∠b = 60° and ∠c = 50° ; find ∠a.

(ii) If ∠a = 100° and ∠b = 55° : find ∠c.

(iii) If ∠a = 108° and ∠c = 48° ; find ∠b.

Calculate the angles of a triangle if they are in the ratio 4: 5: 6.

One angle of a triangle is 60°. The other two angles are in the ratio of 5: 7. Find the two angles.

One angle of a triangle is 61° and the other two angles are in the ratio `1 1/2: 1 1/3`. Find these angles.

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

**Find the unknown marked angles in the given figure:**

### Selina solutions for Concise Mathematics Class 7 ICSE Chapter 15 Triangles Exercise 15 (B)

**Find the unknown angles in the given figure:**

**Find the unknown angles in the given figure:**

**Find the unknown angles in the given figure:**

**Find the unknown angles in the given figure:**

**Find the unknown angles in the given figure:**

**Find the unknown angles in the given figure:**

**Find the unknown angles in the given figure:**

**Apply the properties of isosceles and equilateral triangles to find the unknown angles in the given figure:**

**Apply the properties of isosceles and equilateral triangles to find the unknown angles in the given figure:**

**Apply the properties of isosceles and equilateral triangles to find the unknown angles in the given figure:**

The angle of a vertex of an isosceles triangle is 100°. Find its base angles.

One of the base angles of an isosceles triangle is 52°. Find its angle of the vertex.

In an isosceles triangle, each base angle is four times its vertical angle. Find all the angles of the triangle.

The vertical angle of an isosceles triangle is 15° more than each of its base angles. Find each angle of the triangle.

The base angle of an isosceles triangle is 15° more than its vertical angle. Find its each angle.

The vertical angle of an isosceles triangle is three times the sum of its base angles. Find each angle.

The ratio between a base angle and the vertical angle of an isosceles triangle is 1: 4. Find each angle of the triangle.

In the given figure, BI is the bisector of ∠ABC and Cl is the bisector of ∠ACB. Find ∠BIC.

In the given figure, express a in terms of b.

In Figure, BP bisects ∠ABC and AB = AC. Find x.

Find x in Figure Given: DA = DB = DC, BD bisects ∠ABC and∠ADB = 70°.

In the figure, given below, ABCD is a square, and ∆ BEC is an equilateral triangle. Find, the case:∠ABE

In the figure, given below, ABCD is a square, and ∆ BEC is an equilateral triangle. Find, the case:∠BAE

In ∆ ABC, BA and BC are produced. Find the angles a and h. if AB = BC.

### Selina solutions for Concise Mathematics Class 7 ICSE Chapter 15 Triangles Exercise 15 (C)

**Construct a ∆ABC such that:**

AB = 6 cm, BC = 4 cm and CA = 5.5 cm

**Construct a ∆ABC such that:**

CB = 6.5 cm, CA = 4.2 cm and BA = 51 cm

**Construct a ∆ABC such that:**

BC = 4 cm, AC = 5 cm and AB = 3.5 cm

**Construct a ∆ ABC such that:**

AB = 7 cm, BC = 5 cm and ∠ABC = 60°

**Construct a ∆ ABC such that:**

BC = 6 cm, AC = 5.7 cm and ∠ACB = 75°

**Construct a ∆ ABC such that:**

AB = 6.5 cm, AC = 5.8 cm and ∠A = 45°

**Construct a ∆ PQR such that :**

PQ = 6 cm, ∠Q = 60° and ∠P = 45°. Measure ∠R.

**Construct a ∆ PQR such that:**

QR = 4.4 cm, ∠R = 30° and ∠Q = 75°. Measure PQ and PR.

**Construct a ∆ PQR such that:**

PR = 5.8 cm, ∠P = 60° and ∠R = 45°. Measure ∠Q and verify it by calculations

**Construct an isosceles Δ ABC such that:**

Base BC = 4 cm and base angle = 30°. Measure the other two sides of the triangle.

**Construct an isosceles Δ ABC such that:**

Base AB = 6.2 cm and base angle = 45°. Measure the other two sides of the triangle.

**Construct an isosceles Δ ABC such that:**

Base AC = 5 cm and base angle = 75°. Measure the other two sides of the triangle.

**Construct an isosceles ∆ ABC such that:**

AB = AC = 6.5 cm and ∠A = 60°

**Construct an isosceles ∆ ABC such that:**

One of the equal sides = 6 cm and vertex angle = 45°. Measure the base angles.

**Construct an isosceles ∆ ABC such that:**

BC = AB = 5.8 cm and ZB = 30°. Measure ∠A and ∠C.

**Construct an equilateral Δ ABC such that:**

AB = 5 cm. Draw the perpendicular bisectors of BC and AC. Let P be the point of intersection of these two bisectors. Measure PA, PB, and PC.

**Construct an equilateral Δ ABC such that:**

Each side is 6 cm.

Construct a ∆ ABC such that AB = 6 cm, BC = 4.5 cm and AC = 5.5 cm. Construct a circumcircle of this triangle.

Construct an isosceles ∆ PQR such that PQ = PR = 6.5 cm and ∠PQR = 75°. Using a ruler and compasses only constructs a circumcircle to this triangle.

Construct an equilateral triangle ABC such that it's one side = 5.5 cm. Construct a circumcircle to this triangle.

Construct a ∆ ABC such that AB = 6 cm, BC = 5.6 cm and CA = 6.5 cm. Inscribe a circle to this triangle and measure its radius.

Construct an isosceles ∆ MNP such that base MN = 5.8 cm, base angle MNP = 30°. Construct an incircle to this triangle and measure its radius.

Construct an equilateral ∆ DEF whose one side is 5.5 cm. Construct an incircle to this triangle.

Construct a ∆ PQR such that PQ = 6 cm, ∠QPR = 45° and angle PQR = 60°. Locate its incentre and then draw its incircle.

## Chapter 15: Triangles

## Selina solutions for Concise Mathematics Class 7 ICSE chapter 15 - Triangles

Selina solutions for Concise Mathematics Class 7 ICSE chapter 15 (Triangles) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CISCE Concise Mathematics Class 7 ICSE solutions in a manner that help students grasp basic concepts better and faster.

Further, we at Shaalaa.com provide such solutions so that students can prepare for written exams. Selina textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Concise Mathematics Class 7 ICSE chapter 15 Triangles are Concept for Angle Sum Property, Concept for Exterior Angle Property, Concept for Construction of Simple Triangles., Concept of Triangles - Sides, Angles, Vertices, Interior and Exterior of Triangle.

Using Selina Class 7 solutions Triangles exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in Selina Solutions are important questions that can be asked in the final exam. Maximum students of CISCE Class 7 prefer Selina Textbook Solutions to score more in exam.

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