There is a solution with a concentration of 30%, which is diluted to a solution with a concentration of 20% after adding a certain amount of water. If the same amount of water is added, what will be the concentration?
有浓度为30%的溶液若干，加了一定数量的水后稀释成浓度为20%的溶液，如果再加入同样多的水后，浓度将变为多少．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

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

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(3/10) / (1/5)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">(3/2) - 1</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(3/2) + (1/2)</gadget>
<output>2</output>

<gadget id="calculator">(3/10) / 2</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>