2 sentences

1. 发动机的转速已经达到了每分钟三千转。

   fā​dòng​jī de zhuàn​sù yǐ​jīng dá​dào le měi fēn​zhōng sān​qiān zhuàn.

   The engine speed has reached 3,000 RPM.

   Source: Dong Chinese Dictionary

2. 这种变速电钻可以根据不同的材料调整转速。

   zhè zhǒng biàn​sù diàn​zuàn kě​yǐ gēn​jù bù​tóng de cái​liào tiáo​zhěng zhuàn​sù.

   This variable-speed drill can be adjusted for different materials.

   Source: Dong Chinese Dictionary