After adopting water-saving measures, Hope Primary School used 20 tons of water in May, saving (1/5) compared to April. How many tons of water was used in Hope Primary School in April?
采取节水措施后，希望小学五月份用水20吨，比四月份节约了(1/5)，希望小学四月份用水多少吨？
<gadget id="calculator">1 / 5</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">20 / (4/5)</gadget>
<output>25</output>

<result>25</result>