A vegetable store buys a batch of tomatoes and prices them at a profit rate of 30%. After selling 70%, in order to sell them out as soon as possible, the rest are sold at half the price. What is the profit margin earned by the store after the sale is made? (Profit = Selling Price - Cost, Profit Rate = Profit / Cost * 100%)
某蔬菜商店购进一批西红柿，按30%的利润率定价，卖出70%后，为了尽快销售完，剩下的全部按照定价的半价出售．销售完后，商店获得的利润率是多少？(利润=售价-成本，利润率=利润/成本*100%)
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 + (3/10)</gadget>
<output>13/10 = around 1.3</output>

<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(13/10) * (7/10)</gadget>
<output>91/100 = around 0.91</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(13/10) * (3/10) * (1/2)</gadget>
<output>39/200 = around 0.195</output>

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

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

<gadget id="calculator">(39/200) - 1</gadget>
<output>-161/200 = around -0.805</output>

<gadget id="calculator">(91/100) + (-161/200)</gadget>
<output>21/200 = around 0.105</output>

<result>21/200 = around 0.105</result>