IELTS Grammar: find the mistakes

Here are some sentences that people wrote below Thursday's lesson. Can you find the mistake(s) in each sentence, and explain what the problems are?

1. In 2009, 49% of the trips made by Americans was due to travel to work.
2. In 2009, 49% of the trips made by Americans was for the purpose of moving to work.
3. In 2009, 49% of the trip made by Americans commuter.
4. In 2009, 49% of the trips made by Americans tended to commute to and from work.
5. In 2009, 49% of the trips made by Americans who were to commute to and from work.
6. In 2009, 49% trips made by Americans in order to travel to and from workplace.