In the preparation of "black powder" in ancient my country, the ratio of potassium nitrate, sulfur and charcoal was 15:2:3. Now there are 45 kilograms of charcoal, how many kilograms of "black powder" can be prepared?
我国古代的"黑火药"配制中，硝酸钾、硫磺、木炭的比例为15：2：3．今有木炭45千克，可配制"黑火药"多少千克？
<gadget id="calculator">15 + 2 + 3</gadget>
<output>20</output>

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

<gadget id="calculator">45 / (3/20)</gadget>
<output>300</output>

<result>300</result>