This is one way of doing it, there are plenty of other ways however. If your program works, then it is fine, even if the code is different :)

fun main(){

  val myArrayList: ArrayList<Double> = ArrayList()

  myArrayList.add(13.212312)

  myArrayList.add(23.151232)

  myArrayList.add(32.651553)

  myArrayList.add(16.223817)

  myArrayList.add(18.523999)

  var total = 0.0

  for (i in myArrayList){

    total += i

  }

  var average = total / myArrayList.size

  println("Avarage is " + average)

}