To celebrate New Year's Day, Teacher Wang bought 64 balls, of which red balls accounted for 25%, the ratio of red balls to blue balls is 4:5, how many blue balls are there?
为了庆祝元旦，王老师买了64个球，其中红球占25%，红球和蓝球的比是4：5，蓝球有多少个？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">64 * (1/4) * (5/4)</gadget>
<output>20</output>

<result>20</result>