Page 184 - ICSE Math 7

¾ The medians of a triangle meet at a common point known as the centroid.

¾ The altitudes of a triangle are concurrent (i.e., they meet at a point). This point is known as the
orthocentre.

¾ The sum of the three angles of a triangle is 180°.
¾ The exterior angle of a triangle is equal to the sum of its two interior opposite angles.
¾ In a right-angled triangle, the side opposite to the right angle is known as the hypotenuse and
the other two sides are called its legs.
¾ In a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the
other two sides.

MENTAL MATHS

1. Choose the correct answer.
(a) A triangle whose angles measure 40°, 40° and 100° is a/an ________ triangle.
(i) scalene (ii) right (iii) isosceles (iv) equilateral

(b) In a scalene triangle, if from the same vertex a median and an altitude is drawn to the opposite
side, then the measure of median is ________ the measure of altitude.
(i) less than (ii) greater than
(iii) equal to (iv) half of

(c) The two legs of a right-angled triangle measure 12 cm and 35 cm. What is the length of its
hypotenuse?
(i) 100 cm (ii) 37 cm (iii) 10 cm (iv) 7 cm
(d) Which of the following is a Pythagorean triplet?
(i) 2, 3, 5 (ii) 4, 5, 7 (iii) 7, 24, 25 (iv) 11, 35, 37

(e) What is the area of a square having diagonal l cm?

2
(i) l cm 2 (ii) l 2 cm 2 l
2
2
2
(iii) 2 l cm (iv) none of these
2. Write True or False.
(a) A right-angled triangle can never be obtuse.

(b) A triangle can have two obtuse angles.
(c) The median of a triangle always lies inside the triangle.
(d) The point of intersection of altitudes may lie outside the triangle.

3. Fill in the blanks.
(a) In a triangle, the line joining the vertex to the midpoint of the opposite side is known as
____________.
(b) The perpendicular drawn from the vertex of a triangle to the opposite side is known as
___________.
(c) The three medians of a triangle meet at a ______________ known as the _______________.

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