Page 192 - ICSE Math 6

AT A GLANCE

¾ A simple closed figure made up of line segments only is called a polygon.
¾ A triangle is a three sided polygon and a quadrilateral is a four sided polygon.

¾ On the basis of sides, triangles are classified as equilateral triangles, isosceles triangles and
scalene triangles.

¾ On the basis of angles, triangles are classified as acute-angled triangles, obtuse-angled triangles
and right-angled triangles.

¾ The hypotenuse of a right-angled triangle is its longest side.
¾ Medians of a triangle join its vertices to the midpoints of the opposite sides.
¾ The perpendicular drawn from the vertex to the opposite side of a triangle is called its altitude.

¾ The centroid is the point of intersection of medians of a triangle and the orthocentre is the point
of intersection of its altitudes.
¾ Parallelogram, rectangle, square, rhombus, trapezium and kite are the different types of
quadrilaterals.

MENTAL MATHS

1. Write True or False.
(a) Every rectangle is a parallelogram.

(b) A rhombus is also a parallelogram.
(c) Adjacent sides of a parallelogram are equal.

(d) A triangle is a polygon having four sides.
(e) A triangle has three sides and three vertices.

(f) Triangles can be classified on the basis of their vertices.
(g) The median of a triangle always lies inside the triangle.

(h) The point of intersection of altitudes may lie outside the triangle.
2. Fill in the blanks.

(a) A polygon having 5 sides is called a __________.
(b) A polygon is said to be regular if all of its __________ are equal in length and all of its
__________ are equal in measure.

(c) A simple closed figure made up of line segments only is called a __________.
(d) A polygon having least number of sides is a __________.

(e) A quadrilateral has __________ sides.
(f) The adjacent sides of a rectangle are __________.

(g) A quadrilateral with one pair of parallel sides is a __________.
(h) If in DPQR, PQ = QR ≠ PR, then DPQR is _________ triangle.

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