
RS Aggarwal Solutions for Class 8 Maths Chapter 15 Exercise 15.1: The Physics Wallah academic team has produced a comprehensive answer for Chapter 15 Quadrilaterals in the RS Aggarwal class 8 textbook. The RS Aggarwal class 8 solution for chapter 15 quadrilaterals Exercise-15A is uploaded for reference only.
Before going through the solution of chapter 15 quadrilaterals Exercise-15A, one must have a clear understanding of the chapter 15 quadrilaterals. Read the theory of chapter 15 quadrilaterals and then try to solve all numerals of exercise-15A.RS Aggarwal Solutions for Class 8 Maths Chapter 15 Exercise 15.1 PDF
(1) Fill in the blanks:
(i) A quadrilateral has four sides. (ii) A quadrilateral has four angles. (iii) A quadrilateral has four vertices, no three of which are collinear . (iv) A quadrilateral has two diagonals. (v) A diagonal of a quadrilateral is a line segment that joins two opposite vertices of the quadrilateral. (vi) The sum of the angles of a quadrilateral is 360 o .(2) In the adjoining figure, ABCD is a quadrilateral.
(i) How many pairs of adjacent sides are there? Name them.
Ans: Four; (AB, BC), (BC, CD), (CD, DA), (DA, AB)(ii) How many pairs of opposite sides are there? Name them.
Ans: Two; (AB, DC), (AD, BC)(iii) How many pairs of adjacent angles are there? Name them.
Ans: Four, (∠A, ∠B), (∠B, ∠C), (∠C, ∠D), (∠D, ∠A)(iv) How many pairs of opposite angles are there? Name them.
Ans: Two; (∠A, ∠C), (∠B, ∠D)(v) How many diagonals are there? Name them.
Ans: Two; (AC, BD)(3) Prove that the sum of a quadrilateral is 360 o .
Solution: Let ABCD be a quadrilateral. Join AC.
Clearly, ∠1 + ∠2 = ∠A ……….(i)
And, ∠3 + ∠4 = ∠C ………..(ii)
We know that the sum of the angles of a triangle is 180
o
.
∴ From ∆ ABC, we have
∠1 + ∠3 + ∠B = 180
o
From ∆ACD, we have
∠1 + ∠3 + ∠D = 180
o
Adding the angles on either side, we get:
∠2 + ∠4 + ∠B + ∠1 + ∠3 + ∠D = 360
o
⇒ (∠1 + ∠2) + ∠B + (∠3 + ∠4) + ∠D = 360
o
⇒ ∠A + ∠B + ∠C + ∠D = 360
o
(proved)
(4) The three of a quadrilateral are 76 o , 54 o and 108 o . Find the measure of the fourth angle.
Solution: Let the measure of the fourth angle be x o . ∴ 76 + 54 + 108 + x = 360 ⇒ x + 238 = 360 ⇒ x = 360 – 238 ⇒ x = 122 Hence, the measure of the fourth angle is 122 o .(5) The angles of a quadrilateral in the ratio 3 : 5 : 7 : 9. Find the measure of each of these angles.
Solution: Let the angles of the quadrilateral are 3x, 5x, 7x and 9x. ∴ 3x + 5x + 7x + 9x = 360 ⇒ 24x = 360 ⇒ x = 15 Therefore, measure of each angles are 3 × 15 = 45 o 5 × 15 = 75 o 7 × 15 = 105 o 9 × 15 = 135 o .(6) A quadrilateral has three acute angles, each measuring 75 o . Find the measure of the fourth angle.
Solution: Let the measure of the fourth angle be x o . ∴ x + (75 × 3) = 360 ⇒ x + 225 = 360 ⇒ x = 360 – 225 ⇒ x = 135 Therefore, measure of the fourth angle is 135 o .(7) Three angles of a quadrilateral are equal and the measure of the fourth angle is 120 o . Find the measure of each of equal angles.
Solution: Let the measure of each equal angle be x o . ∴ x + x + x + 120 = 360 ⇒ 3x = 360 – 120 ⇒ 3x = 240 ⇒ x = 80 Therefore, the measure of each of the equal angle is 80 o .(8) Two angles of a quadrilateral measure 85 o and 75 o respectively. The other two angles are equal. Find the measure of each of these equal angles.
Solution: Let the measure of each equal angle be x o . ∴ x + x + 85 + 75 = 360 ⇒ 2x + 160 = 360 ⇒ 2x = 360 – 160 ⇒ 2x = 200 ⇒ x = 100 Therefore, the measure of each equal angle is 100 o .(9) In the adjacent figure, the bisectors of ∠A and ∠B meet in a point P. If ∠C = 100 o and ∠D = 60 o , find the measure of ∠APB.
Solution: Here,
But, ∠BAP + ∠ABP + ∠APB = 180
o
⇒ 100
o
+ ∠APB = 180
o
⇒ ∠APB = 180
o
– 100
o
= 80
o
Clear Conceptual Understanding: The solutions provide detailed explanations of different types of quadrilaterals, helping students grasp fundamental concepts and properties such as parallel sides, equal angles, and diagonal relationships.
Structured Approach: Each problem is solved step-by-step, allowing students to follow a logical progression and understand the methodology required for solving various quadrilateral-related problems.
Formula Application: The exercise emphasizes applying formulas for calculating the sum of interior angles and other specific properties of quadrilaterals, reinforcing mathematical reasoning and analytical skills.
Enhanced Problem-Solving Skills: By practicing diverse problems, students develop critical thinking and problem-solving abilities, essential for tackling more complex mathematical concepts in higher classes.
Exam Preparation: The solutions align with the curriculum and exam patterns, providing practice questions that help students prepare effectively for exams and improve their performance.
