Stupid error in JS that I can;t find

 document.write("This task is for creating and editing various types of arrays. <br>");
      document.write("First,we create an integer array with random numbers. <br>");
      var rngarray = [Math.floor(Math.random(1,10)*10),Math.floor(Math.random(1,10)*10),Math.floor(Math.random(1,10)*10),Math.floor(Math.random(1,10)*10),Math.floor(Math.random(1,10)*10)];
      document.write("Here is a rng array:" + rngarray + ". <br>");
      var rngpowerof3 = [];
      document.write("Now we power the rng array elements by 3. <br>");
      for(i = 0;i<rngarray.length;i++)
      {
          rngpowerof3[i] = Math.pow(rngarray[i],3);
      }
      document.write("The final result is: " + rngpowerof3 +  " . <br>");
      document.write("Now we create random array of marks. <br>");
      var rngmarks = [Math.floor(Math.random(2,6) * 10),Math.floor(Math.random(2,6) * 10),Math.floor(Math.random(2,6)*10),Math.floor(Math.random(2.6)*10),Math.floor(Math.random(2,6) *10),Math.floor(Math.random(2.6)*10)];
      document.write("The array is the following: " + rngmarks + ". <br>");
      var marksbetween3and4 = [];
      document.write("Now we collect the marks between 3 and 4. <br>");
      for(i = 0;i<rngmarks.length;i++)
      {
          if(rngmarks[i] >= 3 && rngmarks[i] <= 4)
          {
              marksbetween3and4.push(rngmarks[i]);
          }
      }
      document.write("Here is the result: " + marksbetween3and4 + " . <br>");
      document.write("Now we make the sum and the multiplication of the square roots of the first random number array. <br>");
      var rngarraysquareroot = [];
      var rngarraysquarerootmult = 0;
      var rngarrsquarerootsum = 0;
      for(i = 0;i<rngarray.length;i++)
      {
         rngarraysquareroot[i] = Math.floor(Math.sqrt(rngarray[i]));
         rngarraysquarerootmult *= rngarraysquareroot[i];
         rngarraysquarerootsum += rngarraysquareroot[i];
      }
      document.write("Here are the results: <br> The square root integer array is: " + rngarraysquareroot + " <br>" + " The multiplication of square roots is: " + rngarraysquarerootmult + " <br>" + "The sum of square roots is: " + rngarraysquarerootsum + " <br>");