Answer:
29 m
Explanation:
The dashes mean that the lines are equal in length, so from this we can determine that the area marked 441 m² is a square.
Area of a square = x², where x is the length of 1 side.
Therefore, x = √441 = 21 m
Now we have a right-angled triangle with two legs of 20 m and 21 m. We need to find the hypotenuse (labelled ?). To do this, use Pythagoras' Theorem a² + b² = c², where a and b are the legs and c is the hypotenuse.
Therefore,
20² + 21² = c²
⇒ 400 + 441 = c²
⇒ 841 = c²
⇒ c = √841
⇒ c = 29
So the side marked ? on the diagram is 29