Among the 15 even numbers 2, 4, 6, ..., 30, randomly select 9 numbers, and prove that the sum of two of them must be 34.
2、4、6、…、30这15个偶数中，任取9个数，证明其中一定有两个数之和是34．
<gadget id="calculator">4 + 30</gadget>
<output>34</output>

<result>34</result>