A garment factory produces a batch of school uniforms. The ratio of the number of sets completed in the first 8 days to the total number of this batch of school uniforms is 1:3. If another 120 sets are produced, 60% of this batch of school uniforms will be completed. How many sets of school uniforms are there in total?
服装厂生产一批校服，前8天完成的套数与这批校服总套数的比是1：3，如果再生产120套，正好完成这批校服的60%．这批校服共多少套？
<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(3/5) - (1/3)</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">120 / (4/15)</gadget>
<output>450</output>

<result>450</result>