2 sentences for 投机 (tóu​jī — speculate)

1. 股市在狂热的投机中不断攀升。

   gǔ​shì zài kuáng​rè de tóu​jī zhōng bù​duàn pān​shēng.

   The stock market kept climbing amidst feverish speculation.

   Source: Dong Chinese Dictionary

2. 这些商人企图通过投机倒把来牟取暴利。

   zhè​xiē shāng​rén qǐ​tú tōng​guò tóu​jī dǎo​bǎ lái móu​qǔ bào​lì.

   These merchants attempted to make huge profits through speculation and profiteering.

   Source: Dong Chinese Dictionary