The diagram is not drawn to scale.


But you can tell from the middle part , that one long side of the triangle is 3 times the length of the short side.

(The long side and short sides are perpendicular (at 90°) to each other.
We are not looking at the longest slanted side (also known as the hypotenuse) here)


So if you let the short side be 1 unit,
Then long side = 3 units

Perimeter of rectangle
= 4 long sides + 4 short sides
= 4 × 3 units + 4 × 1 unit
= 12 units + 4 units
= 16 units
= 96 cm

1 unit
= 96 cm ÷ 16
= 6 cm

So 1 long side
= 6 cm × 3
= 18 cm

Area of 1 triangle

= ½ × base × height
= ½ × 6 cm × 18 cm
= 54 cm²

Alternatively,


Length of rectangle

= 2 short sides + 1 long side
= 2 units + 3 units
= 5 units
= 5 × 6 cm
= 30cm

Breadth of rectangle

= 1 long side
= 3 units
= 18cm


Area of rectangle = 30 cm × 18 cm = 540 cm²

Area of 1 triangle = 540 cm² ÷ 10 = 54 cm²