IELTS Grammar: singular or plural after %

I was surprised to see how many people made the mistake below:

49% of the trips made by Americans was for...

We need to use "were" instead of "was". When you have a percentage, the verb needs to agree with the noun that comes after it. For example:

- 50% of people were happy with the service. ('people' is plural)
- 50% of the project was completed last year. ('project' is singular)