The fertilizer plant used 4,500 kWh of electricity in May, which was 500 kWh less than in April. How much was the saving?
化肥厂五月份用电4500度，比四月份节约了500度，节约了百分之几？
<gadget id="calculator">4_500 + 500</gadget>
<output>5_000</output>

<gadget id="calculator">500 / 5_000</gadget>
<output>1/10 = around 0.1</output>

<result>1/10 = around 0.1</result>