A batch of watermelons was shipped from a certain fruit market, and 40% of the total was sold on the first day, leaving 900 kilograms. How many kilograms are there in total for this batch of watermelons?
某水果市场运来一批西瓜，第一天卖出了总数的40%，还剩900千克．这批西瓜共有多少千克？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">900 / (3/5)</gadget>
<output>1_500</output>

<result>1_500</result>