Final answer:
The specific percentage is not provided, but working smoke alarms and residential sprinkler systems are highly effective in reducing the risk of death in a home fire.
Step-by-step explanation:
The combination of working smoke alarms and a residential sprinkler system significantly reduces the risk of death in a home fire.
While your question does not provide the specific percentage, research and data from organizations like the National Fire Protection Association often indicate high levels of effectiveness when both systems are in place.
Insurance companies recognize this and may offer lower rates for properties that maintain a minimum level of security and have fire sprinkler systems installed and regularly inspected. Moreover, these measures can be seen as a way of reducing moral hazard in the insurance industry.