Teacher Wang bought 20 rulers, paid 15 yuan, and got back 1.6 yuan. How much is each ruler?
王老师买20把尺子，付出15元，找回1.6元，每把尺子多少元？
<gadget id="calculator">15 - 1.6</gadget>
<output>13.4</output>

<gadget id="calculator">13.4 / 20</gadget>
<output>0.67</output>

<result>0.67</result>