A factory consumes 420 kwh of electricity in May, saving 10% compared to the plan. What is the correct formula for the planned kwh of electricity consumption?
某工厂五月份用电420度，比计划节约10%，求计划用电多少度的正确列式是多少
<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">420 / (9/10)</gadget>
<output>1_400/3 = around 466.666667</output>

<result>1_400/3 = around 466.666667</result>