Add 4.5 kg of water to dilute salt water with a salt content of 5% to obtain a salt water with a salt content of 0.5%. How many kilograms of salt water are there now?
把含盐率为5%的盐水，加入4.5千克的水稀释成含盐率为0.5%的盐水，求现在有盐水多少千克？
<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">4.5 * (1/20)</gadget>
<output>0.225</output>

<gadget id="calculator">0.5 / 100</gadget>
<output>0.005</output>

<gadget id="calculator">(1/20) - 0.005</gadget>
<output>0.045</output>

<gadget id="calculator">0.225 / 0.045</gadget>
<output>5</output>

<result>5</result>