Answer
HK = 20 cm
Step-by-step explanation
The Pythagoras Theorem is used for right angled triangle, that is, triangles that have one of their angles equal to 90 degrees.
The side of the triangle that is directly opposite the right angle or 90 degrees is called the hypotenuse. It is normally the longest side of the right angle triangle.
The Pythagoras theorem thus states that the sum of the squares of each of the respective other sides of a right angled triangle is equal to the square of the hypotenuse. In mathematical terms, if the two other sides are a and b respectively,
a² + b² = (hyp)²
For this question,
a = HJ = 16 cm
b = JK = 12 cm
hyp = HK = ?
a² + b² = (hyp)²
16² + 12² = HK²
256 + 144 = HK²
400 = HK²
HK² = 400
Take the square root of both sides
√(HK²) = √(400)
HK = 20 cm
Hope this Helps!!!