The school renovated the library, with an actual investment of 36,000 yuan, which was 9,000 yuan less than the planned investment. How much was saved.
学校装修图书馆，实际投资3.6万元，比计划投资节约了0.9万元．节约了多少．
<gadget id="calculator">3.6 + 0.9</gadget>
<output>4.5</output>

<gadget id="calculator">0.9 / 4.5</gadget>
<output>0.2</output>

<result>0.2</result>