factory used 5,400 tons of water in the second half of April, saving 20% compared with the first half of April. How many tons of water was used in the first half of April?
某工厂四月份下半月用水5400吨，比上半月节约20%，上半月用水多少吨？
<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">5_400 / (4/5)</gadget>
<output>6_750</output>

<result>6_750</result>