There are 10 different locks, and the 10 keys to open the 10 locks are mixed together. How many times can you try to match all the 10 locks with the keys?
有10把不同的锁，开这10把锁的10把钥匙混在一起了，最多要试多少次，才能把这10把锁和钥匙全部配对．
<gadget id="calculator">9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1</gadget>
<output>45</output>

<result>45</result>