There are three piles of balls A, B and C. If B is 20% more than A and C is 10% less than A, how much is C less than B?
有三堆球A，B和C，如果B比A多20%，C比A少10%，那么C比B少多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(6/5) - (9/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(3/10) / (6/5)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>