Question

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

Answer 1

Answer:

3rd Side42-(18+10) = 14 cm

s = 42/2=21

area=v 21x3x11x7=69.6cm2

Answer 2

$\Large{\textbf{\underline{\underline{According\;to\;the\;Question}}}}$

Given,

Sides of Triangle = (18 and 10)cm

Also,

Perimeter = 42 cm

Now,

Assume,

Sides be p = 18 cm, q = 10 cm

Also,

Third side = r cm

Perimeter of a triangle = p + q + r

42 = 18 + 10 + r

42 = 28 + r

r = 42 - 28

r = 14

So,

Third side (r) = 14 cm

Now,

Semi Perimeter :-

s = (a + b + c)/2

s = (18 + 10 + 14)/2

s = 42/2

s = 21 cm

Now,

Using Heron formula :-

A = √s (s - a) (s - b) (s - c)

A = √21(21 - 18)(21 - 10)(21 - 14)

A = √21 × 3 × 11 × 7

A = √(3 × 7) × (3) × (11) × (7)

A = √(3 × 3) × (7 × 7) × (11)

A = 3 × 7√ 11

A = 21√11 cm²

Therefore,

Area of triangle = 21√11 cm²