Answer:
y = 40 / sqrt(pi)
Explanation:
The area is 400
We want to find the diameter
400 = pi r^2
Divide each side by pi
400/ pi = r^2
Take the square root of each side
sqrt(400/ pi) = sqrt(r^2)
20/ sqrt(pi) = r
The diameter is twice the radius
2 r = d
2 * 20/ sqrt(pi) = d
40 / sqrt(pi) =d
y is the diameter so
y = 40 / sqrt(pi)