Type A tissue is 9.6 yuan for 20 packs. Buy 20 packs of Type B tissue and get 10 packs for free. The price is 15.9 yuan. Which one is cheaper? How much is it cheaper per packet?
甲种纸巾20包9.6元，乙种纸巾买20包赠10包，售价15.9元，那种便宜？每小包便宜多少元？
<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">15.9 / 30</gadget>
<output>0.53</output>

<gadget id="calculator">9.6 / 20</gadget>
<output>0.48</output>

<gadget id="calculator">0.53 - 0.48</gadget>
<output>0.05</output>

<result>0.05</result>