The perimeter of a triangle is calculated by adding its three side lengths.
We are given two side lengths of the triangle, 11mm and 35mm, but are missing the third. Note that the side whose length is missing is the hypotenuse of the right triangle formed to the left of the diagram.
For this right triangle, the lengths of the legs are 25mm and 23mm. Let's substitute these values in the Pythagorean Theorem and solve for the hypotenuse c.
Please note that since c is the hypotenuse of a right triangle it must be non-negative, which is why we only kept the principal root when solving the equation. The length of the hypotenuse is 34.0mm to the nearest tenth. This is also the length of the third side of the triangle for which we want to find the perimeter.
Now we can add the three side lengths to obtain the perimeter.
Perimeter: 11+35+34.0=80.0mm
Area
The area of a triangle is half the product of its base and its height. The height is the altitude perpendicular to whichever side is being used as the base.
In the given triangle, we can see that the base is 11mm and that the height is 25mm. We can substitute these two values in the formula for the area of a triangle and simplify.
