The wholesale price of T-shirts is 30 yuan each, and buy 5 get 1 free. How much does it cost to buy 30 pieces?
T恤衫批发价每件30元，并且买5送1．如果买30件需多少元钱．
<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">30 * (5/6) * 30</gadget>
<output>750</output>

<result>750</result>