def present_to_future_value(ir, t):
    """
    Returns a coefficient to convert money from one point in time to
    t years in the future, with an annual interest rate of ir. This is
    the inverse of future_to_present_value if calculated with the same
    rate and number of years.
    Example:
    >>> round(present_to_future_value(.07,10),7)
    1.9671514
    >>> round(present_to_future_value(.07,10)*        future_to_present_value(.07,10),7) == 1
    True
    """
    return (1 + ir) ** t
