A repeater is sold for 100 yuan after the price is reduced by (1/5). What is the correct formula for the original price of the repeater?
一种复读机，降价(1/5)后，卖100元，求这中复读机的原价是多少元的正确列式是多少
<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">100 / (4/5)</gadget>
<output>125</output>

<result>125</result>