What is the smallest fraction that can be divided by the fractions (6/7), (5/14), (10/21) and the results are all integers.
能被分数(6/7)，(5/14)，(10/21)除得的结果都是整数的最小分数是多少．
<gadget id="calculator">30 / 7</gadget>
<output>30/7 = around 4.285714</output>

<result>30/7 = around 4.285714</result>