A batch of coal is shipped from the boiler room of a certain factory. According to the daily consumption of 150 kg of coal in the old boiler, it can be used for 120 days. If a new boiler is used, the coal consumption will be reduced by 20%. How many more days can this batch of coal be burned?
某工厂锅炉房运来一批煤，按旧锅炉每天用煤150千克，可用120天，如改用新锅，耗煤量将减少20%，这批煤可以多烧多少天？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">150 * (4/5)</gadget>
<output>120</output>

<gadget id="calculator">120 / 120</gadget>
<output>1</output>

<gadget id="calculator">150 * 1</gadget>
<output>150</output>

<gadget id="calculator">150 - 120</gadget>
<output>30</output>

<result>30</result>