Usages of sìshí
现在 交通 很 发达， 从 郊区 到 市中心 的 地铁 常常 很 满， 要 坐 四十 分钟， 比 公交车 方便。xiànzài jiāotōng hěn fādá, cóng jiāoqū dào shìzhōngxīn de dìtiě chángcháng hěn mǎn, yào zuò sìshí fēnzhōng, bǐ gōngjiāochē fāngbiàn.
Transportation is very developed now; the subway from the suburbs to downtown is often very full and takes forty minutes, but it’s more convenient than the bus.
我 在 这 个 城市 住 了 四十 天 了。wǒ zài zhè gè chéngshì zhù le sìshí tiān le.
I have lived in this city for forty days.
这 次 考试 至少 要 写 三十 个 句子， 很多 人 最后 写 了 超过 四十 个 句子。zhè cì kǎoshì zhìshǎo yào xiě sānshí gè jùzi, hěnduō rén zuìhòu xiě le chāoguò sìshí gè jùzi.
For this exam you have to write at least thirty sentences; many people ended up writing more than forty.
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