The perimeter of the bottom of an oil barrel is a square of 6 decimeters, and the depth of the barrel is 3 decimeters. Now there are 4.5 liters of oil in the barrel. How many liters of oil can be contained in the barrel?
一个油桶的底面周长是6分米的正方形，桶深是3分米，现在桶中有油4.5升，桶中还能装多少升油？
<gadget id="calculator">6 / 4</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">(3/2) * (3/2) * 3</gadget>
<output>27/4 = around 6.75</output>

<gadget id="calculator">(27/4) - 4.5</gadget>
<output>2.25</output>

<result>2.25</result>