A supermarket buys a basket of apples, first takes out 210 apples, and then takes out (3/5) of this basket of apples. At this time, the ratio of the number of remaining apples to the original total number is 1:6. How many apples were there originally?
某超市购进一筐苹果，先拿出210个，再拿出这筐苹果的(3/5)，这时剩下的苹果的个数与原来总个数的比是1：6，这筐苹果原来共有多少个？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (1/6) - (3/5)</gadget>
<output>7/30 = around 0.233333</output>

<gadget id="calculator">210 / (7/30)</gadget>
<output>900</output>

<result>900</result>