The store can make a profit of 12 yuan for each calendar sold. It is known that each calendar sells for 52 yuan. What is the profit rate of this kind of calendar?
商店每卖出一本挂历，可获得利润12元，已知每本挂历售价52元，这种挂历的利润率为多少．
<gadget id="calculator">52 - 12</gadget>
<output>40</output>

<gadget id="calculator">12 / 40</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(3/10) * 1</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>