Find the remaining sides of a 45°-45°-90° triangle if the longest side is 20.

45°-45°-90° is an isosceles right triangle. The longest side is hypotenuse.
All 45°-45°-90° triangles have sides that are in a unique ratio. The two legs are the exact same length, and the hypotenuse is that length times the √2.

Let a be the leg then hypotenuse = a√2.

You have 2 sides that are 2 cms and you have 6 sides that are 1/2 cm and you have 4 sides that are 1 cm. the smallest sides are 1/2 the medium sized sides are 1 and the smallest are 1/2. so to find the perimeter you have to add them all up together so your answer will be 11 cm's