def second_smallest(numbers):
    """Returns the second smallest number

    :param numbers: (list) List of numbers of at least size 2
    :return: (int or float) The second smallest number
    """
    numbers.sort()
    return numbers[1]


# Leave this part for easily testing your function
print('[6, 3, 9, 2, 1] second_smallest returns', second_smallest([6, 3, 9, 2, 1]))
print('[23, 23.25, 23.5, 23] second_smallest returns', second_smallest([23, 23.25, 23.5, 23]))