Grandpa Li’s house used 120 degrees of electricity in May, which was 30 degrees less than the original plan. How much did Grandpa Li’s house save electricity in May?
李爷爷家五月份用电120度，比原计划节约30度，李爷爷家五月份用电节约了百分之几？
<gadget id="calculator">120 + 30</gadget>
<output>150</output>

<gadget id="calculator">30 / 150</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>