const arr = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'];

let win = 0;
let trails = 10000000;
for (let i = 0; i < trails; i++) {
  if (arr[Math.floor(Math.random() * arr.length)] === '0') {
    win += 50;
  }
  if (arr[Math.floor(Math.random() * arr.length)] === '0') {
    win += 30;
  }
  for (let k = 0; k < 8; k++) {
    if (arr[Math.floor(Math.random() * arr.length)] === '0') {
      win += 10;
    }
  }
}
console.log(win / trails);