The railway corps excavated a cave with a length of 168m. The original plan was to complete the task in 24 days, but it was actually completed 4 days earlier than the original plan. How much more meters were dug per day than originally planned?
铁道兵开凿一个长168m的山洞，原计划24天完成任务，实际比原计划提前4天完成．实际每天比原计划多开凿多少米？
<gadget id="calculator">24 - 4</gadget>
<output>20</output>

<gadget id="calculator">168 / 20</gadget>
<output>42/5 = around 8.4</output>

<gadget id="calculator">168 / 24</gadget>
<output>7</output>

<gadget id="calculator">(42/5) - 7</gadget>
<output>7/5 = around 1.4</output>

<result>7/5 = around 1.4</result>