Language: C++

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

#define EPS 1e-10

struct Point {
	double x, y;

	Point() {}
	Point(double x, double y) :x(x), y(y) {}

	Point operator+(const Point& p) const { return Point(x + p.x, y + p.y); }
	Point operator-(const Point& p) const { return Point(x - p.x, y - p.y); }
	Point operator*(const double& k) const { return Point(x * k, y * k); }
	Point operator/(const double& k) const { return Point(x / k, y / k); }

	friend istream& operator>>(istream& is, Point& p) {
		is >> p.x >> p.y;
		return is;
	}
};

typedef Point Vector;

double norm(Vector a) { return a.x * a.x + a.y * a.y; }
double abs(Vector a) { return sqrt(norm(a)); }

struct Circle {
	Point c;
	double r;

	Circle() {}
	Circle(Point c, double r) :c(c), r(r) {}
};

double arg(Vector p) { return atan2(p.y, p.x); }
Point polar(double a, double r) { return Point(cos(r) * a, sin(r) * a); }

vector<Point> getCrossPointCC(Circle c1, Circle c2) {
	double d = abs(c1.c - c2.c);
	double a = acos((c1.r * c1.r + d * d - c2.r * c2.r) / (2 * c1.r * d));
	double t = arg(c2.c - c1.c);
	vector<Point> ps;
	ps.push_back(c1.c + polar(c1.r, t + a)); ps.push_back(c1.c + polar(c1.r, t - a));
	return ps;
}

int main() {
	int N, K; cin >> N >> K;
	vector<Point> ps(N);
	vector<double> c(N);
	for (int i = 0; i < N; ++i) cin >> ps[i] >> c[i];
	double l = 0, r = 1e9;
	for (int _ = 0; _ < 300; ++_) {
		double mid = (l + r) / 2;
		bool flag = false;
		for (int i = 0; i < N; ++i) {
			int cnt = 0;
			for (int j = 0; j < N; ++j)
				if (abs(ps[i] - ps[j]) <= mid / c[j] + EPS) ++cnt;
			if (cnt >= K) flag = true;
		}
		for (int i = 0; i < N; ++i) {
			Circle A(ps[i], mid / c[i]);
			for (int j = i + 1; j < N; ++j) {
				Circle B(ps[j], mid / c[j]);
				if (abs(A.c - B.c) >= A.r + B.r) continue;
				if (abs(A.c - B.c) < abs(A.r - B.r)) continue;
				auto ccp = getCrossPointCC(A, B);
				int cnt1 = 0, cnt2 = 0;
				for (int k = 0; k < N; ++k) {
					if (abs(ccp[0] - ps[k]) <= mid / c[k] + EPS) ++cnt1;
					if (abs(ccp[1] - ps[k]) <= mid / c[k] + EPS) ++cnt2;
				}
				if (cnt1 >= K || cnt2 >= K) flag = true;
			}
		}
		if (flag) r = mid;
		else l = mid;
	}
	printf("%.10f\n", r);

	return 0;
}

Compiler output:
a.cc: In function 'double abs(Vector)':
a.cc:29:31: error: 'sqrt' was not declared in this scope
   29 | double abs(Vector a) { return sqrt(norm(a)); }
      |                               ^~~~
a.cc: In function 'double arg(Vector)':
a.cc:39:31: error: 'atan2' was not declared in this scope
   39 | double arg(Vector p) { return atan2(p.y, p.x); }
      |                               ^~~~~
a.cc: In function 'Point polar(double, double)':
a.cc:40:48: error: 'cos' was not declared in this scope
   40 | Point polar(double a, double r) { return Point(cos(r) * a, sin(r) * a); }
      |                                                ^~~
a.cc:40:60: error: 'sin' was not declared in this scope
   40 | Point polar(double a, double r) { return Point(cos(r) * a, sin(r) * a); }
      |                                                            ^~~
a.cc: In function 'std::vector<Point> getCrossPointCC(Circle, Circle)':
a.cc:44:20: error: 'acos' was not declared in this scope
   44 |         double a = acos((c1.r * c1.r + d * d - c2.r * c2.r) / (2 * c1.r * d));
      |                    ^~~~