def strike_temp(ambient_temp, target_temp, ratio):
    """
    Calculate the temperature of the strike liquor
    :param ambient_temp: [float] Ambient temperature in any units (both temps
    must agree)
    :param ratio: [float] desired ratio in quarts / pound
    :param target_temp: [float] Target wort resting temperature
    :return: [float] strike temperature in units given
    """
    return (target_temp - ambient_temp) / (5 * ratio) + target_temp