2012的倒数是______．
∵2012×12012=1，
∴2012的倒数是12012．
故答案为：12012．
The number of students who took part in the competition last week ________ more than 1500.
A．reach
B．were
C．is
D．was
用一根机械效率为90%的杠杆将一个18Kg的物体提升50cm，则所做的有用功为 _________ J，总功为_________J（g取10N/kg）
