Question

Find the area of an isoceles triangle where perimeter is 11cm and base is 5 cm

Answer 1

since it is an isosceles triangles, other two sides ( except base ) must be same.
let's take p as perimeter
a, b are two same length sides, so lets take the length be x.
c is the base.
since,
$p = a + b + c$
11 = x + x + 5
x = 3

Now you have all the three sides.
a = b = 3
c = 5

Now area of a triangle formula of HERON
$area \: = \: \sqrt{s(s - a)(s - b)(s - c)}$
Here s is semi perimeter

$s = p \div 2$
Now you can easily calculate the area.
Hope it helps,

Have a great day.