他在股市中投机赚了很多钱。
tāzài gǔshì zhōng tóujī zhuànle hěnduō qián 。
He speculated in the stock market and made a lot of money.
这种投机行为在经济上是不稳定的。
zhèzhǒng tóujī xíngwéi zài jīngjì shàng shìbù wěndìng de 。
This kind of speculative behavior is unstable economically.
他的意见虽然投机，但也很有道理。
tāde yìjiàn suīrán tóujī ， dàn yě hěn yǒudàolǐ 。
His opinions are speculative, but they also make a lot of sense.