There are eight numbers lined up, their average is 54, the average of the first five numbers is 46, the average of the last four numbers is 68, what is the fifth number.
有八个数排成一列，它们的平均数是54，前五个数的平均数是46，后四个数的平均数是68，第五个数是多少．
<gadget id="calculator">46 * 5</gadget>
<output>230</output>

<gadget id="calculator">68 * 4</gadget>
<output>272</output>

<gadget id="calculator">230 + 272</gadget>
<output>502</output>

<gadget id="calculator">54 * 8</gadget>
<output>432</output>

<gadget id="calculator">502 - 432</gadget>
<output>70</output>

<result>70</result>