A cup of salt water weighs 21 kilograms and has a concentration of 7%. When 0.7 kilograms of pure salt is added, what is the concentration of this cup of salt water?
一杯盐水重21千克，浓度是7%，当再加入0.7千克的纯盐后，这杯盐水浓度是多少？
<gadget id="calculator">7 / 100</gadget>
<output>7/100 = around 0.07</output>

<gadget id="calculator">21 * (7/100)</gadget>
<output>147/100 = around 1.47</output>

<gadget id="calculator">(147/100) + 0.7</gadget>
<output>2.17</output>

<gadget id="calculator">21 + 0.7</gadget>
<output>21.7</output>

<gadget id="calculator">2.17 / 21.7</gadget>
<output>0.1</output>

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

<gadget id="calculator">0.1 * 1</gadget>
<output>0.1</output>

<result>0.1</result>