During the holiday, Xiaoming's family sailed on a yacht. When returning, the speed was slowed down by 20% due to the headwind. It is known that the power energy of the yacht can only be used for 5.4 hours at a time. How many hours should the yacht return after leaving?
假日里，小明一家驾着游艇去航行，返回时，因逆风速度要减慢20%．已知游艇的动力能源一次只能用5.4小时，问游艇最多开出几小时后就应该返回？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">5.4 * (4/9)</gadget>
<output>2.4</output>

<result>2.4</result>