21. A circular fountain is located at the center of a square park. The shortest distance from the edge of the fountain to each side of the park is exactly 10 meters. If the diagonal of the park measures 40 meters, what is the approximate area, in square meters, of the circular fountain?
Explanation
We are given a square park with a circular fountain at its center. The shortest distance from the edge of the fountain to each side of the park is 10 meters, and the diagonal of the square park is 40 meters. Graphically, it looks like this:
Calculating the Fountain's Dimensions We can find the side length of the square park using the given diagonal and Pythagorean theorem:
side² + side² = diagonal²
2 · side² = (40)²
side² = 1600 / 2
side = √800
The entire side length of the square minus the shortest distance from the edge of the fountain to each side of the park (which is 10 meters from each side) gives us the diameter of the fountain. So, the diameter of the fountain is:
diameter = side - 10 - 10
diameter = √800 - 20
The radius of the fountain is half of its diameter, so:
radius = (√800 - 20) / 2 ≈ 4.142
Finally, we can calculate the area of the circular fountain using the formula A = πr² :
area = πr²
= π(4.142)²
area = 53.9
Therefore, the correct answer is Choice A.
Explanation
We are given a square park with a circular fountain at its center. The shortest distance from the edge of the fountain to each side of the park is 10 meters, and the diagonal of the square park is 40 meters. Graphically, it looks like this:
Calculating the Fountain's Dimensions We can find the side length of the square park using the given diagonal and Pythagorean theorem:
side² + side² = diagonal²
2 · side² = (40)²
side² = 1600 / 2
side = √800
The entire side length of the square minus the shortest distance from the edge of the fountain to each side of the park (which is 10 meters from each side) gives us the diameter of the fountain. So, the diameter of the fountain is:
diameter = side - 10 - 10
diameter = √800 - 20
The radius of the fountain is half of its diameter, so:
radius = (√800 - 20) / 2 ≈ 4.142
Finally, we can calculate the area of the circular fountain using the formula A = πr² :
area = πr²
= π(4.142)²
area = 53.9
Therefore, the correct answer is Choice A.