Question

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

Answer 1

a+b+c=42
18+10+c=42
c=42-18
therefore third side is 24 cm.
now find the area of triangle by the herons formula.

Answer 2

Hi,

Here's ur answer:-

The unknown side = 42-(18+10)=42-28=14 cm

We can use Heron's formula here to find area.

If perimeter = 42

s = 1/2× perimeter = 1/2× 42= 21 cm

Heron's formula:-

$\sqrt{s(s - a)(s - b)(s - c)}$
Here a,b,c are sides of the triangle.

so, according to the formula,

$\sqrt{21(21 - 18)(21 - 10)(21 - 14)}$
=
$\sqrt{21 \times 3 \times 11 \times 7}$
=21√11

So, the area of the triangle is 21√11 cm^2

HOPE IT HELPS (^_^)