Fill a cup with 100 grams of salt water, pour out 40 grams of salt water, add 40 grams of water, pour out 40 grams of salt water after stirring, and then add 40 grams of water. At this time, the salt content in the cup is 9%. What is the salt content?
一个杯子装了100克盐水，倒出40克盐水，再加40克清水，搅拌后再倒出40克盐水，然后加40克清水，这时杯中盐水含盐率9%，最初杯中盐水含盐率是多少？
<gadget id="calculator">9 / 100</gadget>
<output>9/100 = around 0.09</output>

<gadget id="calculator">(9/100) * 100</gadget>
<output>9</output>

<gadget id="calculator">100 - 40</gadget>
<output>60</output>

<gadget id="calculator">9 / 60</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/20) * 100</gadget>
<output>15</output>

<gadget id="calculator">15 / 60</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) * 100</gadget>
<output>25</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

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