Q# 30 in the given right triangle, find the missing length

Apply the Pythagorean Theorem: a² = b² + c²
Where a is the hypotenuse , b and c are legs of the right triangle 
The missing side is the hypotenuse 
∴ a² = 11² + 17² = 410
∴ a = √410 ≈ 20.2 ft

The correct answer is option 4

Use the Pythagoras theorem to find the unknown side of the right triangle, 

c²=a²+b²

c² = 17²+11²

    = 289+121
   =410

c = √410
   =20.248 ft

To the nearest tenth, 
Answer = 20.2 ft