How much less is the area of a circle with a radius of 3 decimeters than the area of a circle with a radius of 4 decimeters.
半径是3分米的圆的面积比半径是4分米的圆的面积少多少．
<gadget id="calculator">43.75 / 100</gadget>
<output>0.4375</output>

<result>0.4375</result>