Basketball player Zhang Qiang made 30 shots during a shooting practice, and the shooting percentage was just 60%. How many shots did Zhang Qiang miss?
篮球队员张强在一次投篮训练中，命中30球，命中率刚好为60%，问张强有几个球没有投进？
<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">30 / (3/5)</gadget>
<output>50</output>

<gadget id="calculator">50 - 30</gadget>
<output>20</output>

<result>20</result>