What is the large side of a right-angled triangle if its other two sides are 9 cm and 12 cm?

The largest side in a right-angled triangle is called the hypotenuse, and the smaller sides (forming a right angle) are called legs. By the Pythagorean theorem, the sum of the squares of the legs is equal to the square of the hypotenuse, therefore:

a² + b² = c²;

9² + 12² = c²;

81 + 144 = c²;

225 = c²;

c = √225;

c = 15 cm

Answer: 15 cm