There is a glass of 100 grams of 30% salt water, and 20 grams of water is added to it. What is the concentration of the salt water at this time?
有一杯浓度为30%盐水100克，往里面加入20克水，求此时盐水的浓度是多少？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">100 + 20</gadget>
<output>120</output>

<gadget id="calculator">(3/10) / 120</gadget>
<output>1/400 = around 0.0025</output>

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

<gadget id="calculator">100 * (1/400) * 1</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>