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Maths Quiz for Class 8 Understanding Quadrilaterals |
In this post, we are providing 20 online maths quiz
questions for class 8 understanding quadrilaterals. Online maths quiz will take
around 20 minutes to complete it.
Question 1: A polygon with 5 sides is called a __________.
A) triangle
B) quadrilateral
C) pentagon
D) hexagon
Explanation: A polygon with 5 sides is called a pentagon.
Question 2: How many sides are there in a dodecagon?
A) 12
B) 11
C) 10
D) 9
Explanation: There are 12 sides in a dodecagon.
Question 3: Find the number of diagonals in an octagon.
A) 20
B) 18
C) 16
D) 14
Explanation: Number of diagonals in an octagon = n(n – 3)/2 = 8(8 – 3)/2 = 4 × 5 = 20
Question 4: How many diagonals are there in a decagon?
A) 30
B) 35
C) 42
D) 44
Explanation: Number of diagonals in a decagon = n(n – 3)/2 = 10(10 – 3)/2 = 5 × 7 = 35
Question 5: How many sides are there in a quadrilateral?
A) 3
B) 4
C) 5
D) 6
Explanation: A quadrilateral has 4 sides.
Question 6: How many diagonals are there in a quadrilateral?
A) 1
B) 3
C) 2
D) 4
Explanation: Number of diagonals in a quadrilateral = n(n – 3)/2 = 4(4 – 3)/2 = 2 × 1 = 2
Question 7: The sum of the angles of a quadrilateral is ____________.
A) 180°
B) 360°
C) 540°
D) 90°
Explanation: The sum of the angles of a quadrilateral = (n – 2) × 180° = (4 – 2) × 180° = 2 × 180° = 360°
Question 8: Find the sum of the interior angles of an octagon.
A) 540°
B) 720°
C) 900°
D) 1080°
Explanation: The sum of the interior angles of an octagon = (n – 2) × 180° = (8 – 2) × 180° = 6 × 180° = 1080°
Question 9: The three angles of a triangle are 50°, 105° and 80°. Find the measure of the fourth angle.
A) 125°
B) 115°
C) 105°
D) 135°
Explanation: Measure of the fourth angle = 360° – (50° + 105° + 80°) = 360° – 235° = 125°
Question 10: If the measures of the angles of a quadrilateral are in the ratio 4 : 5 : 6 : 3, then find the measures of the greatest angle.
A) 100°
B) 110°
C) 120°
D) 130°
Explanation: The measures of the angles of a quadrilateral are in the ratio 4 : 5 : 6 : 3. Let the measures of the angles be 4x, 5x, 6x and 3x. We know that the sum of the angles of a quadrilateral is 360°. Therefore, 4x + 5x + 6x + 3x = 360° => 18x = 360° => x = 360°/18 => x = 20°. Therefore, the greatest angle = 6x = 6 × 20° = 120°
Question 11: Three angles of a quadrilateral are in the ratio 2 : 6 : 3. The difference of the least and the greatest of angles out of these angles is the fourth angle. Find the measure of the least angle.
A) 24°
B) 48°
C) 72°
D) 60°
Explanation: Three angles of a quadrilateral are in the ratio 2 : 6 : 3. Let the measures of these three angles be 2x, 6x and 3x. Then, the fourth angle = 6x – 2x = 4x. We know that the sum of the angles of a quadrilateral is 360°. Therefore, 2x + 6x + 3x + 4x = 360° => 15x = 360° => x = 360°/15 => x = 24°. Therefore, the measure of the least angle = 2x = 2 × 24° = 48°
Question 12: The sum of the exterior angles of a polygon is ____________.
A) 720°
B) 360°
C) 180°
D) 540°
Explanation: The sum of the exterior angles of a polygon is 360°.
Question 13: Find the measure of each exterior angle of a regular hexagon.
A) 60°
B) 50°
C) 40°
D) 80°
Explanation: The sum of the exterior angles of a regular hexagon is 360°. Therefore, the measure of each angle = 360°/6 = 60°
Question 14: The measure of each exterior angle of a regular polygon is 36°. Find the number of sides in the regular polygon.
A) 7
B) 8
C) 9
D) 10
Explanation: The sum of the exterior angles of a regular polygon is 360°. Therefore, the number of sides in the regular polygon = 360°/36° = 10
Question 15: One angle of a parallelogram measures 75°. Find the measure of the other three angles.
A) 95°, 75°, 95°
B) 100°, 75°, 100°
C) 105°, 75°, 105°
D) 115°, 75°, 115°
Explanation: We know that the opposite sides of a parallelogram are parallel. The adjacent angles of a parallelogram are supplementary. Thus, the adjacent angle of 75° angle = 180° – 75° = 105°. Also, the opposite angles of a parallelogram are equal. Thus, the other three angles are 105°, 75° and 105°.
Question 16: Two adjacent angles of a parallelogram are in the ratio 1 : 1. Find the measures of all the angles of the parallelogram.
A) 80°, 80°, 80°, 80°
B) 90°, 90°, 90°, 90°
C) 60°, 60°, 60°, 60°
D) 90°, 60°, 90°, 60°
Explanation: The adjacent angles of a parallelogram are in the ratio 1 : 1 and they are supplementary. Let their measures be x° each. Thus, x° + x° = 180° => 2x° = 180° => x = 180°/2 => x = 90°. Therefore, the measure of each angle is 90°.
Question 17: If the adjacent sides of a parallelogram are in the ratio 3 : 4 and its perimeter is 70 cm, find the measure of the adjacent sides of the parallelogram.
A) 15 cm, 20 cm
B) 10 cm, 15 cm
C) 12 cm, 18 cm
D) 14 cm, 16 cm
Explanation: Let the adjacent sides be 3x and 4x. Then, perimeter of the parallelogram = 2(3x + 4x) => 70 = 2(3x + 4x) => 70/2 = (3x + 4x) => 35 = 7x => x = 35/7 => x = 5. Thus, the adjacent sides are 3 × 5 and 4 × 5, that is, 15 cm and 20 cm.
Question 18: If the length of a diagonal of a square is 16 cm, find the length of the side of the square.
A) 16 cm
B) 8 cm
C) 8√2 cm
D) 4√2 cm
Explanation: In a square, (diagonals)2 = (side)2 + (side)2 => (diagonals)2 = (x)2 + (x)2 => 2x2 = 162 => 2x2 = 256 => x2 = 256/2 => x2 = 128 => x2 = 64 × 2 => x = 8√2. Thus, the length of the side is 8√2 cm.
Question 19: Find the length of the diagonal of a rectangle with sides 8 cm and 15 cm.
A) 16 cm
B) 17 cm
C) 18 cm
D) 19 cm
Explanation: In a rectangle, (diagonals)2 = (length)2 + (breadth)2 => (diagonals)2 = (8)2 + (15)2 => x2 = 64 + 225 => x2 = 289 => x = 17 cm. Thus, the length of the diagonal is 17 cm.
Question 20: ABCD is a trapezium in which AB is parallel to DC. If ∠A = 70° and ∠B = 80°, then find the measure of its other two angles.
A) 90°, 110°
B) 80°, 100°
C) 110°, 100°
D) 100°, 90°
Explanation: Since AB and DC are parallel, ∠A + ∠D = 180° => 70° + ∠D = 180° => ∠D = 180° – 70° => ∠D = 110°. Similarly, ∠B + ∠C = 180° => 80° + ∠C = 180° => ∠C = 180° – 80° => ∠C = 100°. Thus, the measure of the other two angles are 110° and 100°.
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