Fill in the appropriate number in the box of 3□5□, so that this four-digit number can be divisible by 3 and 5 at the same time, how many different filling methods are there?
在3□5□的方框填上合适的数字，使这个四位数能同时被3和5整除，有多少种不同的填法．
<gadget id="calculator">3 + 3</gadget>
<output>6</output>

<result>6</result>