#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <math.h>

double probOfNoRain(int n,int m); //비 안올확률.
int combination(int a, int b); //a Combination b 를 출력.

int main(int argc, char * argv[]) {
    int t;
    int depth, period;

    scanf("%d", &t);

    while (t--) {
        scanf("%d %d", &depth, &period);

        printf("%.10f\n", (double)1-probOfNoRain(depth - period, period));

    }

    return 0;
}


double probOfNoRain(int n, int m) { // n = depth - period, m = period
    double ret = 0;
    double rain = 0.75;
    double noRain = 0.25;

    for (int i = 0; i < n; i++) {
        ret += (double)combination(m, i)*pow(noRain, m-(double)i)*pow(rain,(double)i); 
    }
    return ret;
}


// 두 자연수를 입력받아 aCb 출력
// aCb = a(a-1)...(a-b+1) / b! = b(b-1)...1

int combination(int a, int b) {
    int i, j, n = 1, r = 1;

    for (i = a; i >= a - b + 1; i--) {
        n = n * i;
    }
    for (j = b; j >= 1; j--) {
        r = r * j;
    }

    return (n / r);
}