Our triangle is ABC with ∠C = 90°
1) AB² = BC² + AC² (Pythagorean theorem)
25² = 20² + AC²
AC² = 625 - 400
AC² = 225
AC = 15
2) PΔABC = AB + BC + AC = 25 + 15 + 20 = 60
3) SΔABC = AC * BC * 1/2 = 15 * 20 * 1/2 = 150
Answer: the perimeter is 60 cm and the area is 150 cm² .
