Sum of multiples of 3 or 5 below 1000 in Scala
In the Scala solution as in the Erlang solution, the accumulator is pointless.  For max = 1000, you don't necessarily have to be concerned about tail recursion, and you could just write it without an accumulator:

def sumMultiplesRecursive(from: Int, to: Int): Int = {
    if (from &gt;= to) {
        0
    } else if (from % 3 == 0 || from % 5 == 0) {
        from + sumMultiplesRecursive(from + 1, to)
    } else {
        sumMultiplesRecursive(from + 1, to)
    }
}


Note that the sum_multiple_recursive name, with underscores, does not follow the Scala naming convention.  It is not so helpful to mention that it works recursively, but it would also be useful to describe what you mean by "multiples".

The from and to parameters, together, could constitute a Range.  If you are going to use a Range, then you might as well take advantage of its capabilities:

def sumMultiplesOf3Or5(range: Range): Int = {
    range.filter(n =&gt; n % 3 == 0 || n % 5 == 0).sum
}

val max = 1000;
println(s"The sum of all the multiples of 3 or 5 below ${max}: " + sumMultiplesOf3Or5(1 until max));