/**
 * Payback Period (PP) is the length of time required to recover the cost of an investment.
 *
 * @see http://www.investopedia.com/terms/p/paybackperiod.asp
 * @param numOfPeriods
 * @param cashFlows
 * @returns
 */
export declare function PP(numOfPeriods: number, cashFlows: number[]): number;