There is a batch of coal that burns 4.5 tons per day and can be burned for 28 days. If you save 0.3 tons per day. How many days can this batch of coal be burned?
有一批煤，每天烧4.5吨，可烧28天．如果每天节省0.3吨．这批煤可以烧多少天？
<gadget id="calculator">4.5 - 0.3</gadget>
<output>4.2</output>

<gadget id="calculator">28 / 4.2</gadget>
<output>6.666667</output>

<gadget id="calculator">4.5 * 6.666667</gadget>
<output>30.000002</output>

<result>30.000002</result>