For a batch of fruit, the remaining mass is 1/3 of the sold fruit mass, and after another 50 kg is sold, the ratio of the remaining mass to the sold mass is 1:4. How many kilograms did this batch of fruit originally have?
一批水果，剩下的质量是卖出的水果质量的(1/3)，又卖出50千克后，剩下的质量与卖出的质量比是1：4．这批水果原来共有多少千克？
<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(4/5) - (3/4)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">50 / (1/20)</gadget>
<output>1_000</output>

<result>1_000</result>