Question

the side of Δ in the ratio 3:5:7 and it's perimeter is 300 m find its area

Answer 1

Let the common ratio be x
Then the sides will be 3x..5x..7x
Perimeter of triangle =sum of all sides
300=3x+5x+7x
300=15x
x=300/15=20 m

So the sides will measure 60 m.. 100m..140m

For calculating it's area..
semi perimeter =60+100+140/2=150 m

Area =under root{s(s-a) (s-b) (s-c)}
=) under root{150(150-60) (150-100) (150-140)}
=)under root(150*90*50*10)
=) 2598.07 m²

Answer 2

we can, let the side of triangle be 3x:5x:7x

now,  3x+5x+7x=300

         15x=300

          x=20  sides are =>  3x=3*20=60 let (a)

                                           5x=5*20=100 let (b)

                                           7x=7*20=140 let (c)

now semiperimeter(s) =60+100+140/2=150

area of triangle will be  root under (s-a)(s-b)(s-c)

                                       root under (150-60)(150-100)(150-140)

                              root under 90*50*10=(5*18)(5*10)(10)=(5*3*3*2)(5*10)(10)

                              150√2 m²        ans.......