Question

find the area of a triangle two sides of which are 18cm and 10cm and the perimeter is 42cm.

Answer 1

Area Of Triangle=1/2×b×h
1/2×18×10
9×10=90cm^2

Perimeter=a+b+c
18+10+c=42
28+c=42
c=42-28
c=14cm

Answer 2

a = 18 cm
b = 10 cm
Perimeter = 42
=> 18+10+ c = 42
=> c = 14 cm

Semi Perimeter = 21 cm
(s-a) = 3
(s-b) = 11
(s-c) = 7


$area \: = \sqrt{s(s - a)(s - b)(s - c)} \\ \: area \: = \sqrt{21 \times 3 \times 11 \times 7 } \\ = \sqrt{7 \times 7 \times3 \times 3 \times 11 } \\ = 21 \sqrt{11}$