Question

Fig. 12.10
4. Find the area of a triangle two sides of which are 18cm and 10cm and the perimeter is
42cm.​

Answer 1

a=18 cm. , b= 10 cm. , perimeter = 42 cm.

Perimeter of the triangle = a+b+c.

42 = 18 + 10 + c.

or. c= 42–28 = 14 cm.

s=(a+b+c)/2 = (18+20+14)/2 cm. = 21 cm.

Area of triangle = √{s.(s-a).(s-b).(s-c)}.

= √{21.(21–18).(21–10).(21–14)}.

= √{21×3×11×7}.

= √{21×21×11}.

= 21√11 sq. cm. or. 69.649 sq.cm. Answer.