There are some coins on the table, some with heads up and some with tails up. At the same time, turn over 25% of the coins with heads up and 25% of the coins with tails up. At this time, the coins with heads up account for 70% of the total. So, what percent of the total number of coins originally landed heads?
桌面上有一些硬币，一部分正面朝上，一部分反面朝上．同时将正面朝上中的25%的硬币翻面，反面朝上中的25%也翻面，这时正面朝上的硬币占总数的70%．那么，原来正面朝上的硬币占总数的百分之几？
<gadget id="calculator">9 / 1</gadget>
<output>9</output>

<gadget id="calculator">9 + 1</gadget>
<output>10</output>

<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(9/10) * 1</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>