Central banks would always try to help the expansion of the economy. If the economy is slowing down, one possible way the central bank could encourage economic expansion is to reduce the interest rate. This makes it less attractive to put the money into bank and people may choose to invest those instead. With a lower interest rate, the businesses may also take this opportunity to borrow money and expand their business. People may also think it is a good time to invest into property for example. So, reducing the interest rate is one such measure.