2018年整理公共英语pets4级精选短语（19）

 　Rule of 72

　　a common formula used to determine the years needed for money to double at compound interest; divide 72 by the interest rate to get the number of years

　　EXAMPLE:

　　According to the rule of 72, $10,000 invested at 6 per cent interest doubles to $20,000 in twelve years.